chile tsunami 2010 case study

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Earthquake and tsunami

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• Why is an earthquake dangerous?
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• Where do earthquakes occur?

Chile earthquake of 2010

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• LiveScience - Chile Quake and Tsunami Dramatically Altered Ecosystems
• Earthquake Engineering Research Institute - The Mw 8.8 Chile Earthquake of February 27, 2010
• Table Of Contents

Chile earthquake of 2010 , severe earthquake that occurred on February 27, 2010, off the coast of south-central Chile , causing widespread damage on land and initiating a tsunami that devastated some coastal areas of the country. Together, the earthquake and tsunami were responsible for more than 500 deaths.

The magnitude-8.8 earthquake struck at 3:34 am . The epicentre was located some 200 miles (325 km) southwest of the Chilean capital of Santiago , and the focus occurred at a depth of about 22 miles (35 km) below the surface of the Pacific Ocean . The earthquake—resulting from the rupture of a 300- to 375-mile (500- to 600-km) stretch of the fault that separates the South American Plate from the subducting Nazca Plate—was felt as far away as São Paolo , Brazil , and Buenos Aires , Argentina . A 2014 study contended that water pressure built up between the two plates had been the catalyst . The initial event was succeeded in the following weeks by hundreds of aftershocks, many of them of magnitude 5.0 or greater. The temblor was the strongest to strike the region since the magnitude-9.5 event of 1960, considered to be the most powerful earthquake ever recorded. ( See Chile earthquake of 1960 .)

Because the region’s violent tectonic history had made it a focus of seismological study and monitoring, extant GPS sensors installed in Chile and neighbouring countries allowed the detection of subtle shifts in the location of cities, including Concepción and even Buenos Aires , as a result of the quake. A NASA computer model ascertained that the powerful force of the subducting plate had shifted Earth ’s axis sufficiently to shorten the day by more than a microsecond. A study of the aftershocks released in 2014 indicated that two anomalously dense rock structures beneath the South American Plate, previously undetected, had likely slowed the rupture and, as a result, intensified shaking at the surface.

Stress brought on by the convergence of the two tectonic plates caused rocks to shatter along the boundary between them. This forced a portion of the seabed upward, displacing the water above and triggering a tsunami . The Chilean town of Constitución was inundated by waves as high as 50 feet (15 metres), and the port of Talcahuano was damaged by a wave measuring nearly 8 feet (2.4 metres) high. Traveling across the Pacific Ocean at nearly 450 miles (725 km) per hour, the tsunami encountered the Juan Fernández Islands , located approximately 420 miles (675 km) off the coast of Chile. Although observers on the largest of the Juan Fernández Islands reported waves as high as 10 feet (3 metres), the tsunami weakened significantly before it reached the coasts of California , Hawaii , New Zealand , and Japan over the next several hours.

A study published in August 2014 noted that the temblor triggered small earthquakes in Antarctica . It was the first direct evidence that earthquakes could trigger secondary seismic events in the Antarctic’s ice sheets.

Though damage to structures within the zone of the earthquake was likely limited by stringent building codes instituted in the wake of the 1960 earthquake and revised several times during the 1990s, many buildings still sustained significant damage, including nearly 400,000 homes. Particularly affected were Maule and Biobío , two first-order administrative districts along Chile’s southern coast. Large areas of Biobío were left without major services, including water, electricity, and gas, and the tall buildings of Concepción —the capital of the district and one of Chile’s largest cities—were among those most severely damaged. Copper production—a major contributor to Chile’s economy—was halted at several mines, though it resumed after limited power was restored the day after the quake. The weakened state of the electrical grid became apparent when large swathes of the country—including Santiago , which had already endured a week without power following the catastrophe—were faced with a daylong blackout in mid-March after a major transformer failed.

Chilean government officials estimated that two million people had been directly affected by the quake. The Chilean National Emergency Office—initially responsible for documenting the casualties—estimated that more than 800 had died. However, as the Interior Ministry reviewed the data in the following weeks, the official total fluctuated significantly as missing persons were located and computational errors were discovered, leading to a reduction of the death toll by hundreds. Official tallies ultimately attributed more than 500 deaths to the disaster; 150 of those casualties were caused by the tsunami. Most fatalities occurred in the Maule district, with further deaths occurring in Biobío and in coastal and island areas damaged by the tsunami. In Concepción the limited availability of food and gasoline led to widespread looting—a phenomenon that later expanded to nonessential items such as televisions—and the consequent arrest of several dozen people. Chilean Pres. Michelle Bachelet arranged for food retailers to distribute necessities free of charge by the next day, but sporadic theft continued into the week as assistance proved slow to arrive. Isolated areas were particularly vulnerable to looting as the need for supplies became increasingly acute .

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Chile Earthquake 2010

At 3.34 am on 27th February 2010, a powerful magnitude 8.8 earthquake occurred just off the coast of central Chile. The earthquake occurred at the destructive plate margin where the South American plate is subducted by the Nazca Plate. The earthquake was followed by a series of smaller aftershocks.

Tsunami warnings were issued as waves originating from the epicentre crossed the Pacific Ocean at speeds of around 800km per hour.

What were the primary effects of the Chile Earthquake?

• Around 500 people died, and 12,000 people were injured. Over 800,000 people were affected.
• Two hundred twenty thousand homes were destroyed, along with 4500 schools, 56 hospitals and 53 ports.
• Santiago airport and the Port of Talahuanao were severely damaged.
• The earthquake disrupted power, water supplies and communications across Chile.
• The cost of the earthquake is estimated to be US$30 billion.

What were the secondary effects of the Chile Earthquake?

• Tsunami waves devastated several coastal towns.
• The tsunami struck several Pacific countries; however, warnings prevented a loss of life.
• A fire at a Santiago chemical plant led to the local area being evacuated.
• Landslides destroyed up to 1500 km of roads, cutting off remote communities for days.

What were the immediate responses to the Chile Earthquake?

• Emergency services responded quickly.
• International support provided field hospitals, satellite phones and floating bridges.
• Within 24 hours, the north-south highway was temporarily repaired, allowing aid to be transported from Santiago to areas affected by the earthquake.
• Within ten days, 90% of homes had had power and water restored.
• US$60 million was raised after a national appeal, which funded 30,000 small emergency shelters.

Damage was done to houses in Concepcion city, Chile, by the 2010 magnitude 8.8 earthquake.

What were the long-term responses to the Chile Earthquake?

• Chile’s government launched a housing reconstruction plan just one month after the earthquake to help nearly affected 200,000 families.
• Chile’s strong economy reduced the need for foreign aid to fund rebuilding.
• The recovery took over four years.

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U.S. Geological Survey Open-File Report 2011–1053, version 1.1

In cooperation with The American Red Cross

Report on the 2010 chilean earthquake and tsunami response, by the american red cross multidisciplinary team.

First posted March 18, 2011

PDF (18 MB) PDF (downsampled to 300 dpi; 1.7 MB)
USGS Multi-Hazard Demonstration Project

.

The delegation was hosted by the Chilean Red Cross and received extensive briefings from both national and local Red Cross officials. During nine days in Chile, the delegation also met with officials at the national, regional, and local government levels. Technical briefings were received from the President’s Emergency Committee, emergency managers from ONEMI (comparable to FEMA), structural engineers, a seismologist, hospital administrators, firefighters, and the United Nations team in Chile. Cities visited include Santiago, Talca, Constitución, Concepción, Talcahuano, Tumbes, and Cauquenes. The American Red Cross Multidisciplinary Team consisted of subject matter experts, who carried out special investigations in five Teams on the (1) science and engineering findings, (2) medical services, (3) emergency services, (4) volunteer management, and (5) executive and management issues (see appendix A for a full list of participants and their titles and teams). While developing this delegation, it was clear that a multidisciplinary approach was required to properly analyze the emergency response, technical, and social components of this disaster. A diverse and knowledgeable delegation was necessary to analyze the Chilean response in a way that would be beneficial to preparedness in California, as well as improve mitigation efforts around the United States. By most standards, the Maule earthquake was a catastrophe for Chile. The economic losses totaled $30 billion USD or 17% of the GDP of the country. Twelve million people, or ¾ of the population of the country, were in areas that felt strong shaking. Yet only 521 fatalities have been confirmed, with 56 people still missing and presumed dead in the tsunami. The Science and Technology Team evaluated the impacts of the earthquake on built environment with implications for the United States. The fires following the earthquake were minimal in part because of the shutdown of the national electrical grid early in the shaking. Only five engineer-designed buildings were destroyed during the earthquake; however, over 350,000 housing units were destroyed. Chile has a law that holds building owners liable for the first 10 years of a building’s existence for any losses resulting from inadequate application of the building code during construction. This law was cited by many our team met with as a prime reason for the strong performance of the built environment. Overall, this earthquake demonstrated that strict building codes and standards could greatly reduce losses in even the largest earthquakes. In the immediate response to the earthquake and tsunami, first responders, emergency personnel, and search and rescue teams handled many challenges. Loss of communications was significant; many lives were lost and effective coordination to support life-sustaining efforts was gravely impacted due to a lack of inter- and intra-agency coordination. The Health and Medical Services Team sought to understand the medical disaster response strategies and operations of Chilean agencies, including perceived or actual failures in disaster preparation that impacted the medical disaster response; post-disaster health and medical interventions to save lives and limit suffering; and the lessons learned by public health and medical personnel as a result of their experiences. Despite devastating damage to the health care and civic infrastructure, the health care response to the Chilean earthquake appeared highly successful due to several factors. Like other first responders, the medical community had the ability and resourcefulness to respond without centralized control in the early response phase. The health care community maintained patient care under austere conditions, despite many obstacles that could have prevented such care. National and international resources were rapidly mobilized to support the medical response. The Emergency Services Team sought to collect information on all phases of emergency management (preparedness, mitigation, response, and recovery) and determine what worked well and what could be improved upon. The Chileans reported being surprised that they were not as ready for this event as they thought they were. The use of mass care sheltering was limited, given the scope of the disaster, because of the resiliency of the population. The impacts of the earthquake and the tsunami were quite different, as were the needs of urban and rural dwellers, necessitating different response activities. The Volunteer Services Team examined the challenges faced in mobilizing a large number of volunteers to assist in the aftermath of a disaster of this scale. One of the greatest challenges expressed was difficulty in communication; the need for redundancy in communication mechanisms was cited. The flexibility and ability to work autonomously by the frontline volunteers was a significant factor in effective response. It was also important for volunteer leadership to know the emergency plans. These plans need to be flexible, include alternative options, and be completed in conjunction with local officials and other volunteers. The Executive/Red Cross Management Team took a broad look at the impacts of the earthquake and the implications for California. Some of the most important preparation for the disaster came from relationships formed before the event. The communities with strong connections between different government services generally fared well. The initial response and resilience of individuals and communities was another important component. Communication system failures limited the ability of a central government to assist impacted communities, or to issue tsunami warnings. It also delayed the response since the government did not know (in some case for several days) the impact and needs of local governments. In general, plans for congregate care shelters existed but were little used as most people chose to stay at damaged homes or with relatives. Looting was a surprise to response officials as well as social scientists, but both public and private sector organizations, including NGOs (Non-Governmental Organizations), must consider security for damaged businesses as a priority in California’s multihazard planning. Class and ethnic divisions that become heightened during some cases of actual or perceived injustice may also emerge in natural disasters in California. Several factors contributed overall to the low casualty rate and rapid recovery. A major factor is the strong building code in Chile and its comprehensive enforcement. In particular, Chile has a law that holds building owners accountable for losses in a building they build for 10 years. A second factor was the limited number of fires after the earthquake. In the last few California earthquakes, 60% of the fires were started by electrical problems, so the rarity of fires may have been affected by the shut down of the electricity grid early in the earthquake. Third, in many areas, the local emergency response was very effective. The most effective regions had close coordination between emergency management, fire, and police and were empowered to respond without communication with the capital. The fourth factor was the overall high level of knowledge about earthquakes and tsunamis by much of the population that helped them respond more appropriately after the event.

Suggested citation:

American Red Cross Multi-Disciplinary Team, 2011, Report on the 2010 Chilean earthquake and tsunami response: U.S. Geological Survey Open-File Report 2011-1053, v. 1.1, 68 p., available at https://pubs.usgs.gov/of/2011/1053/.

1.0 Executive Summary

2.0 Introduction

3.0 Science and Technology

4.0 Emergency Management

5.0 Health Services

6.0 Volunteer Management

7.0 Executive Management

8.0 Recommendations for California

9.0 Recommendations for the American Red Cross

10.0 Sources and Acknowledgments

11.0 Appendices

12.0 Glossary of Terms including Acronyms

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University of Illinois Urbana-Champaign

The Maule (Chile) Earthquake of February 27, 2010: Consequence Assessment and Case Studies

Elnashai, amr s.; gencturk, b.; kwon, o.s.; al-qadi, imad l.; hashash, y.; roesler, jeffery r.; kim, s.j.; jeong, seong-hoon; dukes, j.; valdivia, a..

https://hdl.handle.net/2142/18212 Copy

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• Elnashai, Amr S.
• Gencturk, B.
• Al-Qadi, Imad L.
• Hashash, Y.
• Roesler, Jeffery R.
• Jeong, Seong-Hoon
• Valdivia, A.
• reconnaissance
• field mission
• case studies

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Talcahuano, Chile, in the wake of the 2010 disaster: A vulnerable middle?

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• Published: 28 October 2015
• Volume 80 , pages 1057–1081, ( 2016 )

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• Karen E Engel 1  

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Because of Chile’s geographical position, earthquakes and tsunamis are recurrent phenomena and reducing vulnerability to these events is imperative. To do this, one needs to understand the geophysical features of the hazards involved and the vulnerability that exposed communities live with. This article presents some unexpected findings of a research regarding the latter and devised to investigate the vulnerability realities that the devastating 2010 earthquake/tsunami event in Chile exposed. Interestingly, this study revealed households that are formally considered resilient in the face of natural hazards, but are in fact not. These households are part of a group I call the emergent middle. The ‘middle’ because they are neither rich nor poor, but do not fit the typical middle-class category, and ‘emergent’ because their primary concerns are staying out of poverty and climbing the socioeconomic ladder. The findings of this research suggest that they find themselves in a precarious situation and that their vulnerability to natural hazards largely emerges from their economic fragility and their limited access to relevant resources in the wake of a hazardous event. This article is based on data that were collected through extensive field work in the Greater Concepción area and in particular in Talcahuano that was severely hit in 2010.

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1 Introduction

Because of Chile’s geographical position along the Atacama trench between the Nazca and the South America plates, Chileans are blessed with the beautiful Andes mountain range but are also condemned to face the dangers of recurrent earthquakes and tsunamis. To appraise the extent to which these natural hazards represent a disaster risk, it is important to learn more about both the hazards involved and the vulnerability that exposed communities live with. While numerous studies have examined the geophysical features of earthquakes and tsunamis in Chile (Lomnitz 2004 ; Kiser and Ishii 2011 ; Yamazaki and Cheung 2011 ; Brodsky and Lay 2014 ; Hayes et al. 2014 ; Cisternas et al. 2005 ), only a few have dealt with more societal aspects of vulnerability (Lomnitz 1970 ; Bitar 2010 ; Letelier 2010 ; Mella Polanco 2012 ; Dussaillant and Guzman 2014 ). This study aims to contribute to the body of literature dealing with the latter.

On February 27, 2010, the south-central region of Chile was hit by a magnitude-8.8 Mw earthquake that triggered a devastating tsunami (hereafter 27F, in line with Chilean usage). While disasters are devastating events, they also provide a unique window into the complex interaction between two opposing forces: ‘those processes generating vulnerability on the one side, and the natural hazard event (or sometimes a slowly unfolding natural process) on the other’ (Wisner et al. 2004 : 46). In other words, 27F could be an opportunity to learn more about vulnerability and in particular the coping capacity and resilience of Chilean households vis-à-vis earthquake and tsunami events. With this in mind, the research described in this article was conceived and fieldwork was undertaken in the Biobio region, one of the most affected areas, 2 years after 27F when the dust had settled and evidence of vulnerable conditions had become more discernible.

In the field, some unexpected observations were made. Specifically, this research found households that are neither poor nor rich, and thus find themselves in the middle, that face significant vulnerability to natural hazards such as earthquakes and tsunami. This was rather surprising since middle-class households are typically considered to be ‘affluent homeowners with access to economic resources, insurance, networks of power and influence in the wider community, and social and cultural capital’ (Fordham and Ketteridge 1999 : 27). Only Romero and Vidal ( 2010 ) suggest that middle- and lower-middle-class households were disproportionally negatively affected by the 27F tsunami. In this article, I wish to shed light on the plight of these households. The vulnerability of these households seems to represent a blind spot that cannot be ignored in a country that is continuously beleaguered by a wide variety of natural hazards.

The research from which these findings emerged was not aimed at looking into the socioeconomic aspects of vulnerability. However, as the research advanced it became apparent that some socioeconomic observations could not be ignored, mainly because they were unexpected and in some cases even inconsistent with the literature. Against this background, this article aims to share these findings in order to enhance understanding of some vulnerable realities that exist in Chile so that they can be put on both research and policy agendas and as such can hopefully be adequately addressed in the future.

The data were collected from multiple sources using qualitative methods, i.e., from in-depth, semi-structured and group interviews, observations, participation, formal and informal documents, photographs, films. Data were collected in the field, i.e., ‘at the site where participants experience the issue or problem under study’ (Cresswell 2009 : 175), in the Greater Concepcion area, particularly in Talcahuano, but also in Concepcion and Hualqui, over a period of 6 months in 2012 and 2013 and 5 months in 2014.

Because the aftermath of a disaster is a sensitive topic, especially to those directly affected, for this research I decided to use snowball sampling, which ‘yields a study sample through referrals made among people who share or know of others who possess some characteristics that are of research interest’ (Biernacki and Waldorf 1981 : 141). Using this sampling method, I was able to draw on insiders’ knowledge to locate people who would be willing to recount their stories, which are often hard to tell, for this study. This method enabled me to access a wide variety of people from different socioeconomic backgrounds, ages and even ethnic backgrounds. The respondents in the Greater Concepcion area 47 % were female and 53 % male, aged between 15 and 82. Most respondents were lower, middle or higher middle class (see Fig.  1 ).

Socioeconomic distribution of respondents in the Greater Concepción area and Talcahuano

I conducted formal interviews with 62 respondents, 12 group interviews, and engaged in numerous participation/observation opportunities and professionally engaged with various professional institutions dedicated to disaster risk reduction. As I was completely immersed in life in the Greater Concepcion area, almost every interaction in formal and informal events was useful to my study. The software package ATLAS.ti was used to assist the data analysis.

This article is structured as follows. Section  2 briefly describes the theoretical underpinnings of the study, namely how key concepts such as vulnerability, coping capacity and resilience are viewed. Section  3 introduces the ‘emerging middle’ households in Talcahuano and their exposure to earthquake and tsunami hazards. Section  4 then describes the central findings that support the idea that these households from the ‘emerging middle’ find themselves in a precarious situation vis-à-vis earthquake/tsunami disasters. Finally, Sect.  5 presents some conclusions.

2 Vulnerability

2.1 what is vulnerability.

While the ‘hazards’ or ‘agent-specific’ approach remains dominant, it is increasingly agreed that natural hazards only become disasters when they interact with a vulnerable community: ‘there cannot be a disaster if there are hazards but vulnerability is (theoretically) nil, or if there is a vulnerable population but no hazard event’ (Wisner et al. 2004 : 43; Warner and Engel 2014 ; Birkmann 2006 ). As a result, increasing attention is being given to understanding the vulnerable realities people face vis-à-vis (natural) hazards (Cutter et al. 2008 ). This is easier said than done, however. Although the word ‘vulnerability’ comes from the Latin verb vulnerare (‘to wound’), the disaster literature provides a wide array of definitions, conceptualizations and approaches. Cardona ( 2003 ), for instance, defines vulnerability as ‘the physical, economic, political or social susceptibility or predisposition of a community to damage in the case of a destabilizing phenomenon of natural or anthropogenic origin.’ Cannon et al. ( 2003 : 4–5), on the other hand, emphasizes social vulnerability to highlight that it is about people and their specific characteristics. Vulnerability is not necessarily opposed to coping capacity and resilience but can in fact embrace both. Take, for instance, Watts and Bohle’s ( 1993 ) approach to vulnerability, in which they distinguish three basic coordinates:

The risk of exposure to crises, stress and shocks ( exposure ).

The risk of inadequate capacities to cope with stress, crises and shocks ( capacity ).

The risk of severe consequences of ( potentiality ), and the attendant risks of slow or limited recovery ( resiliency ) from crises, risk and shocks.

Steffen et al. ( 2004 ) adopted a similar approach, in which they define vulnerability as a function of ‘(1) exposure—the degree to which a human group or ecosystem comes into contact with particular stresses, (2) sensitivity—the degree to which an exposure unit is affected by exposure to any set of stresses and (3) resilience—the ability of the exposure unit to resist or recover from the damage associated with the convergence of multiple stresses’ (Steffen et al. 2004 : 205). There are other approaches, however, that view vulnerability, coping capacity and exposure as separate features. Bollin et al. ( 2003 ), for instance, clearly put forward disaster risk as emerging from four independent components, namely hazard, exposure, vulnerability and capacity/measures. I do not subscribe to this latter view as it seems to neglect the complex interactions from which vulnerability emerges. I thus take an approach in line with that of Watts and Bohle.

The key elements of vulnerability, then, are exposure, capacity and resilience. Exposure entails more than spatial exposure and includes social and institutional features, i.e., ‘processes that increase defenselessness and lead to greater danger, such as exclusion from social networks’ (Birkmann 2006 : 19; Watts and Bohle 1993 , Cannon et al. 2003 ). Coping capacity is more straightforwardly defined as ‘[t]he means by which people or organizations use available resources and abilities to face adverse consequences that could lead to a disaster’ (UN/ISDR 2004 : 16–17). Resilience likewise has many conceptualizations and definitions (Engel and Engel 2012 ). For Pelling ( 2003 : loc 1229), resilience is a component of vulnerability and ‘the ability of an actor to cope with or adapt to hazard stress.’

For the purpose of this article, I will use Watts and Bohle’s concept of vulnerability. Since respondents expressed an intrinsic relationship between their experience of vulnerability and their access to and use of specific assets, I will borrow from the livelihood assets of the sustainable livelihood framework (DFID 1999 ) to structure my findings. This pentagon is central to the livelihood framework and allows the important interrelationships between different assets to become more visible (see Fig.  2 ). Because asset endowments change, over time the shape of the pentagon that represents a household’s assets also changes.

Asset pentagons presenting different asset portfolios (DFID 1999 : 5)

Rather than capital stocks in the strict economic sense of the term, these assets should be viewed as the building blocks of sustainable livelihoods. The following assets are included in the pentagon:

Human capital refers to the stock of ‘skills, knowledge, ability to labor and good health that together enable people to pursue different livelihood strategies and achieve their livelihood objectives’ (DFID 1999 : 7). Labor is often used to refer to the flow of human capital or ‘the flow of effort, skill and knowledge that humans directly provide as inputs into productive activities’ (Goodwin 2003 : 5), although for some authors labor resources are subsumed under human capital. Human capital is important because it is key to making use of the other assets.

Social capital refers to ‘the social resources upon which people draw in pursuit of their livelihood objectives’ (DFID 1999 : 9). In other words, these resources are the ‘stock of trust, mutual understanding, shared values, and socially held knowledge that facilitates the social coordination of [productive] activity’ (Goodwin 2003 : 6) upon which people can draw (networks, social claims, social relations, affiliations, associations). Throughout this article, the distinction between bridging (or inclusive) and bonding (or exclusive) social capital is important. Bonding social capital ‘is inward looking and tend[s] to reinforce exclusive identities and homogeneous groups,’ while bridging social capital is ‘outward looking and encompass[es] people across diverse social cleavages’ (Putnam 2000 , chapter 1).

Natural capital is the ‘natural resource stock from which resource flows and services (e.g., nutrient cycling, erosion protection) useful for livelihoods are derived’ (DFID 1999 : 11). Natural capital is made up of a great variety of resources that include intangible public goods such as the atmosphere and biodiversity to divisible assets used directly for production such as trees or land (DFID 1999 : 11). Natural capital is important not just for people who derive their livelihoods from resource-based activities, but for everyone. Human capital, particularly health, for instance, is affected by industrial air pollution.

Physical capital includes ‘the basic infrastructure and producer goods needed to support livelihoods’ (DFID 1999 : 13). Infrastructure entails changes to the physical environment that enable people to meet basic livelihood needs such as affordable transportation, secure shelter and buildings, access to information. Producer goods include the tools and equipment necessary to function productively.

Financial capital refers to the financial resources that people use to achieve their livelihood objectives. As DFID points out, such a definition might not be economically robust since it includes flows as well as stocks and it can contribute to consumption as well as production, although it does capture an important aspect, namely ‘the availability of cash or equivalent, that enables people to adopt different livelihood strategies’ (DFID 1999 : 15); in other words, capital that can be invested in order to produce something, at the very least more money for its owner (e.g., cash, credit/debt, savings).

DFID’s definition of social capital includes vertical networks and connectedness (patron/client) that other authors such as Rakodi ( 1999 : 318) term ‘political capital.’ I would, however, like to make a distinction between social and political capital and refer to social capital as horizontal relations (vis-à-vis peers) and to political capital to identify vertical power relations (e.g., vis-à-vis the state or landlord). Political capital then is increasingly related to power and to ‘the extent to which different groups are aware of their rights and willing and able to assert them’ (Carney 2003 : 42).

2.2 The social and differential nature of vulnerability

Vulnerability is to a significant extent determined by the social, political and economic environment and is thus essentially social since it emerges from these broader patterns of society. Social, political and economic environments ‘operate to generate disasters by making people vulnerable’ (Wisner et al. 2004 : 8). At the same time, vulnerability is differential : Some people are more affected (wounded) by specific hazards than others. So the underlying social (human-made) structures that condition the capacity of specific individuals and groups to respond to, cope with, recover from, ‘adjust to’ or ‘adapt to’ hazards (Cannon 1994 : 14; Hewitt 1995 : 319; Cutter et al. 2003 : 243; Hufschmidt 2011 ).

Since vulnerability is social and differential, the location of a person or group in the social hierarchy influences not just their life experiences, relationships, opportunities and overall life chances (Fothergill and Peek 2004 : 90), but also their vulnerability. Against this background, various vulnerability studies have shown how the poorest stratum of society is generally hardest hit by natural hazards and ‘lose[s] relatively more in disasters… and likewise [has] a more challenging time recovering’ (Phillips et al. 2010 : 86; Beatley 1989 ; Dash et al. 1997 ; Fothergill and Peek 2004 ; Wisner et al. 2004 ; Cannon 1994 ). The position of the poor in the social hierarchy seriously limits their ability to withstand losses, and this stratum is therefore the most vulnerable in the event of a disaster: ‘[l]ivelihoods that provide people with little more than basic needs are unlikely to enable the provision of self-protection, and any associated lack of social protection for such people will result in high levels of vulnerability’ (Cannon 1994 : 24). At the same time, scholars warn that despite the observed high correlation between poverty and vulnerability, ‘vulnerability cannot be read directly off from poverty’ (Wisner et al. 2004 : 12).

Most studies, though, seem to be built on a commonly accepted idea that the poor are the most vulnerable to disasters and that higher strata are not, since they have access to sufficient stocks of capital. These higher strata include households from ‘the middle’ since they have transcended poverty and are thus considered self-reliant and resilient. As a result, their levels of vulnerability are rarely investigated. While this assumption seems widespread and forms the basis of many studies of vulnerability, the question is whether it is correct. Does ‘the middle’ in fact have access to sufficient resources, and are they capable of recovering from a disaster in a timely and satisfactory fashion?

3 The ‘emerging middle’: some observations

Throughout this research, I came across households that were neither rich nor poor, but did not fall neatly into the classic middle-class category in terms of education, job security or purchasing power. They seem to have more in common with what the OECD in Latin America has identified as households from the middle sectors : ‘people in the middle—neither the richest nor the poorest in society…[that] are often quite economically vulnerable, Footnote 1 subject to the risk of falling down the economic ladder’ (OECD 2010 : 15). According to the OECD study, the narrow focus on poverty alleviation has led to a growing number of ‘emerging’ households that are considered to have overcome poverty and are therefore seen as self-sufficient and self-reliant. Arriagada et al. ( 2012 ) also observed this development. They discuss a newly emerged group that cannot necessarily call itself middle class in the traditional sense, but neither is it eligible to benefit from poverty reduction schemes. These households overlap with those that I call households from the ‘emerging middle.’ Their income levels are comparable with those of households in the lower deciles, but the latter receive a significant portion of their income from the government. According to the OECD ( 2010 ), this has created ‘many vulnerable households in the lower reaches of the middle sector that are just over the disadvantaged income threshold’ ( 2010 : 16, 71) and are very vulnerable to ‘even short-term shocks, such as temporary lay-off or a period of illness, [since these] can permanently move them back into poverty in the absence of public support’ (OECD 2010 : 84). To many middle sector households in Chile, the 27F tsunami was such a shock.

Because of the Chilean government’s narrow focus on poverty alleviation the disadvantaged enjoy public benefits, while households from the ‘emerging middle’—who pay taxes and contribute to the existence of public services—do not. As the OECD ( 2010 : 158) exposes, in addition to the limited eligibility of the majority of middle segment households to receive government assistance, the poor quality of public services compels them to spend significant portions of their income on private education and/or health care for their families, ‘even where the extra cost is a significant additional burden on household budgets’ (OECD 2010 : 166). To these households, these costs are important investments. Education, for instance, is often seen as essential to improve social mobility and thus represents an investment in future generations. In addition, over the past 20 years, the level of over-indebtedness of middle-class households has risen substantially as they have taken advantage of the lax rules on the availability of credit. This ‘has led to over-indebtedness in these social groups, from the D to the C2, due to consumer loans for mortgages or children’s education’ (Barozet and Fierro 2011 : 31). Indebtedness makes ‘the middle’ even more vulnerable as the substantial costs or ‘investments,’ largely in education and health care, in combination with indebtedness, leads to increasing distress as feelings of financial insecurity rise.

What I also learned about these households from the emerging middle at least the ones from my study is that they seem to share some values. Throughout the interviews it became clear that they find hard work, effort and sacrifice important values, especially in light of their primary objective, which is to improve their socioeconomic situation. For instance, many remarked that, whenever possible, they were willing to pay the extra costs of private healthcare and/or educational opportunities, even if it meant taking out a loan that would take decades to repay. To them these are investments in opportunities for their children and grandchildren, even if stretching their resources in effect also means increasing their overall vulnerability.

It seems that the precarious position of this group in Chile is also closely related to persistently high levels of economic inequality and social differentiation in terms of access to social services such as schools, hospitals and housing, and to opportunities more generally (Larrañaga 2009 : 13; Solimano 2011 ; 2012 ). Even though Chile has enjoyed significant economic growth and poverty has declined, it faces important challenges that, according to Solimano ( 2011 ; 2012 ), persist as genuine attempts to introduce reforms, improve incomes and wealth distribution, and increase social protection are constrained by ‘the high concentration of economic power and political influence of the dominant elites that block any serious attempt to shift income distribution to the middle income and the working poor.’

In addition, there is some controversy about the accuracy of the actual poverty figures used by the government. In 2008 , the economist Felipe Larrain published a study in which he reassessed the official poverty figures by generating a new consumption basket using a household consumption study of 1996–1997. The cost of the new basket was 51 % higher than that of the basket used to define the official poverty line for 2006, which was based on consumption patterns in the 1980s and thus did not reflect recent demographic and economic changes. Based on this reassessment, Larrain arrived at a poverty rate of 29 %, more than double the official rate of 13.7 %. This begs the question of whether some of the households currently considered middle class should in fact be reclassified as poor.

It is important to note that these challenges are accompanied by an overall feeling of discontent that is not helped by a political system that remains ‘a highly elitist affair with low degrees of social participation in public decision-making’ (Solimano 2011 : 9). Also, as Cleuren has observed, ‘Chilean politics are marked by low levels of citizen participation, and the recently created participatory initiatives are only instrumental without a genuine commitment of the government to open up the decision-making process to its citizens’ (Cleuren 2007 : 14). This has resulted in low levels of trust in government institutions and political parties. According to a survey by the Centro de Estudios Públicos, only 17 % of respondents stated that they have significant trust in the government and a mere 3 % in political parties. The municipalities scored a little better, with 22 %. Such low levels of trust were also reflected in the 2010–2014 World Values Survey, in which 52 % of respondents stated that they have little or no faith in the government and 80 % have little to no faith in political parties (WVS 2014 ). As Solimano ( 2011 ) observed, these challenges make social cohesion in Chile very elusive.

The households discussed here also share similarities with those that Barozet and Fierro ( 2011 ) consider middle class. For instance, they also find a segment of the middle sector to which hardly any public policies are directed and who find it difficult to ask and receive assistance because they consider it beneath their dignity: ‘while the poor and more popular segments [of society] can receive and look for state assistance, because of their precarious situations, the Chilean middle sectors either do not qualify for assistance because they have certain resources or simply find it difficult to ask for assistance because they feel it implies lowering themselves’ ( 2011 : 26). The latter idea that receiving assistance is equivalent to lowering oneself I also found throughout my interviews. I learned that to my respondents state assistance had a negative connotation and was often associated with handouts for the needy; as one respondent told me, ‘nobody wants to be “el pobrecito” (the little needy one)’ (interview, 2013). In their eyes, state assistance is not something that citizens might be entitled to in times of unforeseen adverse events, for instance, or an indicator of good governance.

The households that I refer to as the ‘emerging middle’ also appear to overlap with the D and Cb segments in the Esomar Nivel Socio Economico (socioeconomic) marketing scale (Adimark 2000 , hereafter NSE Esomar). This letter-based stratification scale classifies households based on two variables, the educational level and occupation of the household’s principal provider, which together determine the NSE of a household. There are five categories:

higher middle,

lower middle.

4 The impact of 27F in Chile, the Biobio region and Talcahuano

Because of Chile’s geographical position, strong earthquakes accompanied by substantial tsunamis are recurrent phenomena (Silbergeit and Prezzi 2012 ). Consequently, Chile has a significant seismic history, present and future, with ‘a magnitude 7 [earthquake] every 5 years, and a magnitude 4 occurring five times a week’ (Earthquake Engineering Research Institute 2010 : 6). One of the regions that is most often struck by strong earthquakes and tsunamis is the Biobio region. This can be explained by its location along ‘the younger portion of the 5000 km subduction zone, where the Nazca plate dives fast with a stronger coupling (tight sticking that causes strong friction between the two plates) with the overriding plate’ (Aon 2010 : 4).

The relatively high frequency of earthquakes has moved Chileans to develop a variety of mechanisms to deal with the often adverse effects. For instance, even though internationally it is advised to ‘duck, cover, hold’ when an earthquake strikes, Chileans tend to escape their homes as quickly as they possibly can. This behavior was observed as long ago as 1904, and my interviews suggest that it remains the primary instinctive course of action: ‘[Chilean] inhabitants avoid bodily harm by escaping from their homes because of any moderately perceptible shaking, since there is no telling what might follow; and this praiseworthy custom has been the more successful, as strong shocks are generally preceded by lighter ones’ (Goll 1904 ). According to a study by Lomnitz, this course of action has been successful at saving lives: ‘the average out-of-doors is safer than the average indoors [and] [r]apid evacuation of dwellings has been effective in preventing or reducing earthquake casualties’ (Lomnitz 1970 : 1312). In addition to effective behavior, Chile has also seen great advances in the construction of earthquake-resistant buildings that enable survival even if earthquakes are so strong that standing up and leaving are impossible. This was the case with 27F. The magnitude-8.8 Mw earthquake was so strong that many people were thrown to the floor while trying to escape.

Tsunamis occur significantly less frequently than earthquakes, and as a result there seem to be fewer coping mechanisms. The primary coping mechanism used by coastal communities is based on local knowledge that when a major earthquake strikes (one above magnitude-7.5 Mw) you should run up the nearest hill. While I was unable to find out where and how this local knowledge developed, I did come across the story of origin of the Mapuches (Bengoa 2000 ), the indigenous people of south-central Chile. Their story begins with a major flood that Mapuches survived because Ten Ten, a snake that lived in the hills, advised them to run up the hill whenever CaiCai, a great snake that lived in the sea, made the sea waters rise. Those who got up the hill survived, while those who did not were transformed into fish. While I did not find a direct connection, it seems that the local knowledge that moved people to run up the nearest hill in response to 27F could have its roots in this story. Since 27F and the large number of deaths caused by the tsunami, Chile is moving toward more tsunami mitigation and preparedness. The municipality of Talcahuano, for instance, is working on evacuation routes and locations (see Fig.  3 ), increasing tsunami awareness and preparedness, and has built a significant number of supposedly tsunami-resistant dwellings.

Talcahuano ( Source Google Maps)

The powerful earthquake that struck Chile at 03:34:17 on February 27, 2010, triggered a substantial tsunami that severely impacted 700 km of the south-central coastline (Aon 2010 : 10) and caused damage as faraway as California (Information Collection Assessment Team 2010 ). The main shock was so powerful that it shortened a normal day on earth by 1.26 μs and moved the city of Concepción 3 m to the west and the capital Santiago 28 cm to the west-southwest (Information Collection Assessment Team 2010 ; Aon 2010 ). For many coastal localities, the tsunami caused most of the destruction. The overall impacts of 27F were significant—562 lives were lost, 75 % of Chileans were affected, 2 million of them directly, over 200,000 homes were destroyed, and the economic losses have been estimated at US$ 30 billion (EM-DAT  2015 ; Gobierno de Chile 2010 : 5). Furthermore, the main shock was followed by numerous aftershocks, ‘including over 130 magnitude 6 or higher aftershocks within the following week’ (Technical Council on Lifeline Earthquake Engineering 2010 , 1). In fact, a magnitude 6.9 aftershock startled guests and journalists just before Sebastian Piñera was to be sworn in as president (Barrionuevo 2010 ).

Talcahuano, an important port city in the Biobio region, was severely affected by both the earthquake and the tsunami. In total, 37 people lost their lives (21 due to the tsunami), 53,637 people were affected, 1956 dwellings were severely damaged while 6442 suffered minor damage, and 1805 people had to find shelter in camps and 380 in other locations (PNUD 2012 : 13).

The tsunami that hit Talcahuano consisted of three waves. The first wave, with a run-up of 5 m (the vertical height of the wave above sea level at its furthest point inland), occurred half an hour after the main seismic shock. The second wave was smaller, with a run-up of 3 m, and reached Talcahuano at 5:15 am. The third wave was the largest, with a run-up of 6 m, and hit Talcahuano at 7:30 am (Quezada et al. 2012 ; La Tercera 2015 : 12). A thick fog covered the city and it was still dark, so few people actually saw the waves. They just heard ‘a nasty sound of dragging iron,’ which later turned out to be the noise of containers and shipping vessels being dragged onshore into the city. Only at daybreak, when the fog dissipated, did people realize what had happened. Aside from destruction, the tsunami deposited a thick layer of oily debris: ‘there was a disgusting blubber…it must have been all the dirt that was on the sea floor…Petrol, fish and other kinds of residue…It was disgusting cleaning it up and it took months to get it all out’ (interviews 2013). As one professional diver remarked, ‘after the tsunami, the ocean was lovely since it had been cleansed’ (interview 2013).

5 Vulnerability in Talcahuano

This research unveiled a group of households from the emerging middle that were not just economically fragile, but in the wake of 27F proved significantly vulnerable to natural hazards. Their vulnerability to natural hazards seems to have primarily emerged from a disproportionate exposure to tsunamis and a limited access to important resources that inhibit their coping capacity and resiliency. Throughout these paragraphs, I will elaborate on these findings. Since my respondents indicated the particular importance of four forms of capital, namely natural, financial, social and political capital, I will borrow these from the sustainable livelihood approach to guide the discussions.

5.1 Exposure

Throughout my research, it quickly became apparent that in Talcahuano some households from the ‘emerging middle’ in particular are experiencing increasing exposure to tsunamis. This was first brought to my attention by one of my respondents, who remarked that Talcahuano had also been affected by a tsunami in 1960 but that it had been largely contained by the area where the Santa Clara neighborhood now stands. This and various other neighborhoods have been built on wetlands that used to absorb and disperse tidal surges and thus damp down the adverse effects of tsunamis. Today, however, these wetlands have been infilled and the area is occupied by families from the middle who were unaware of the tsunami risk they were exposing themselves to by moving to these neighborhoods. In fact, Santa Clara was one of the neighborhoods most affected by the 27F tsunami (UNDP 2011 : 27, 2012 : 25). That particularly households from the middle are exposed to tsunamis is confirmed when putting together a tsunami risk map and a socioeconomic map of Talcahuano. Footnote 2 Here one sees the predominance of middle- and lower-middle-class households in tsunami-exposed areas (see Fig.  4 ).

A tsunami risk map and socioeconomic map of Talcahuano revealing the exposure of households to tsunamis ( Sources Municipal Disaster Risk Management Department; National Congressional Library)

This helps to explain Romero and Vidal’s ( 2010 ) finding that middle- and lower-middle-class households were disproportionally negatively affected by the 27F tsunami (see Fig.  5 ).

Socioeconomic distribution of homes in Talcahuano affected by the 27F tsunami ( Source Romero and Vidal 2010 )

Investigating this further, it came to light that Talcahuano has been built on two types of territory: a peninsula and an isthmus. The peninsula is high ground and together with the hills on the isthmus is often referred to as ‘the hills.’ To the east of the isthmus, also known as the isthmus of the Low Lands, lies the Rocuant wetland, which is colloquially referred to as ‘the plain’ (see Fig.  6 ). The isthmus houses approximately two-thirds of the population of Talcahuano and, together with the bays along the shores of the peninsula, is exposed to tsunamis.

Talcahuano: ‘the hills,’ the isthmus and the Rocuant wetland ( Source Own elaboration with Google earth)

Most neighborhoods on ‘the hills’ are unplanned settlements that over time have been normalized by local authorities. Because of their unplanned nature, there are few basic services, such as schools, health care and police presence, and are located at considerable distances from job opportunities, commercial centers and transportation. These neighborhoods are commonly regarded as marginal and unsafe. For instance, when I asked my respondents from the emerging middle whether they would consider moving there they would tell me that was not an option since people there are different and there are fewer opportunities. In terms of their exposure to tsunamis, however, ‘the hills’ are safe.

The majority of ‘the plain’ is wetlands. Historically, these wetlands served to absorb tsunamis and reduce their impact (interviews 2013; Vidal and Romero 2010 : 1; Bucci 2013 ) and were not allowed to be urbanized. Throughout the second half of the twentieth century, however, the city experienced significant growth (since 1970 the urban area of Talcahuano has doubled). The demographic pressure, in combination with the liberalization of the land market, eventually led to the urbanization of areas exposed to natural threats, like tsunamis and flooding (Vidal and Romero 2010 : 11). The development of the wetlands was attractive to real-estate companies since building on (steep) hills is technically more complex and thus more expensive (Pauchard et al. 2005 : 274). So when the land market was liberalized and permission was granted to develop previously restricted areas, real-estate companies jumped at the opportunity to buy and develop the wetlands cheaply and sell homes at profitable margins (interviews Talcahuano 2013–2014), even though this meant doing away with Talcahuano’s mitigation area and placing more people at risk: ‘In 1960 we had a tsunami here in Talcahuano, but it was largely absorbed by the area where I now live’ (interviews Talcahuano 2013). Real-estate companies endorsed the commonly accepted idea that wetlands were wasteland that could provide a greater public service if drained and filled in (Pauchard et al. 2005 : 274). Since then large parts of Talcahuano’s wetlands have been used to develop residential areas, and they continue to be urbanized.

These new residential areas were perfect for young families aspiring to a better way of life with access to basic services, commercial centers and transportation. As a result, by 2010, these neighborhoods were occupied by a large number of households I have labeled ‘the middle.’ These households had no idea that this upward movement would come at the expense of increasing their exposure to natural hazards. They assumed that the (local) authorities would never allow the development of unsafe land and the subsequent sale of ‘unsafe’ houses, just as they do not permit the sale of unsafe goods in supermarkets. To what extent this assumption was false became apparent in the wake of 27F.

Even though the respondents residing on the wetlands expressed they were unaware of their exposure, coastal communities know that in case of a real earthquake, i.e., of more than 7.5 Mw, they should climb the nearest hill. This latent knowledge that is part of a greater disaster subculture (Engel et al. 2014 ) saved many people so that the number of deaths in Talcahuano due to the tsunami was limited. Still some people died, mainly either because they did not believe a tsunami would affect them or because the authorities assured them there was no threat and they should return to their tsunami-exposed homes.

While some households have resettled since 27F, most residents do not want to leave. The households that were part of this study revealed they felt strong ties to their neighborhoods. They revealed that these feelings were primarily related to the time and energy they had invested in developing a perfect living situation for their families. From what I have seen, in the Greater Concepción area it is common to buy a home at an early stage of family life which can be expanded in time and in such a way as to provide the family with the right living conditions, including the social and built environment. Over time, these investments result in unique homes that are tailor-made and satisfy all the family’s specific needs. Against this background, leaving becomes undesirable. Leaving implies leaving behind the product of years of effort, sacrifice and financial investment. Moreover, interviews revealed that often these families do not have the resources to start all over. For instance, households from this study expressed that moving to ‘the hills’ is not an option, largely because of the prevalence of poverty and high crime rates and the distance to resources and services. Leaving would thus entail a decreased sense of security on a daily basis, and putting at risk the access to relevant resources they do have. Leaving would, for example, mean losing a social environment that for many is key to their household’s resilience. In other words, the households that are discussed here continue to live in neighborhoods that are substantially exposed to tsunamis.

5.2 Natural capital

The rapid urbanization and industrialization of Talcahuano has had a negative impact on the environment. For instance, for decades waste was dumped indiscriminately, particularly into the sea. However, as a Balinese once told me, the sea always returns whatever is dumped in its waters. This seems to have been the case in Talcahuano, as the retreating tsunami left a thick black micro layer of oily waste containing high concentrations of bacteria, viruses, toxic metals and organic pollutants on shore. The wetland areas affected by the tsunami were also covered by this layer, and the pollutants it contained were to some extent absorbed into the soil. Few studies have been done to determine the extent of the contamination so that residents are unaware of the potential risks they face residing on this contaminated land (interviews 2013, Fariña et al. 2012 ).

In addition to the contamination, the residents of the wetland neighborhoods are exposed to several other risks. Infilled wetlands tend to amplify earthquake waves due to their ‘soft’ soils and sediments. Such amplification can result in greater damage. In addition, wetlands tend to suffer from liquefaction, which ‘involves the temporary loss of strength of sands and silts which behave as viscous fluids rather than soils … when seismic waves pass through a saturated granular layer of uncohesive sediments, distorting the granular structure and causing some of the void spaces to collapse’ (Alexander 1999 : chapter 4) and ‘[w]idespread liquefaction-induced ground deformation and related damage to soils and foundations occur to spectacular and devastating effect in almost every strong earthquake’ (Huang and Yu 2013 ). Liquefaction can thus have significant consequences, such as ‘the collapse of foundations or the settling of structures’ (Alexander 1999 : chapter 4). During the 27F earthquake, ‘several coastal and river vicinities experienced extensive liquefaction…’ (Technical Council on Lifeline Earthquake Engineering 2010 : 6). Because liquefaction can cause catastrophic failures in building structures (Verdugo 2012 : 708), Alexander ( 1999 : chapter 4) has argued that it is best to avoid building on such susceptible terrains.

The wetland neighborhoods of Talcahuano have already experienced liquefaction and will continue to do so in the future. Because of the lack of comprehensive studies of the state of the soil beneath the wetland neighborhoods, it remains unclear to what extent the soil has been negatively affected by the 27F earthquake and tsunami. The consequences include increasing exposure to the dangers associated with liquefaction in the event of future earthquakes. Much remains unknown, but it is clear that residing on infilled wetlands in a region that is repeatedly subjected to strong earthquakes and tsunamis entails exposure to a variety of substantial dangers.

Infilling wetlands for the development of residential areas for the ‘emerging middle’ households has not just enhanced their exposure, but has also reduced the stock of natural capital available to provide protective services and subsequently decrease the probability of a disaster occurring or reducing the damage in case of an event, that is, the wetlands enabling flood control and mangroves attenuating wave and storm surges (Kousky 2010 ). Combine this with the contamination and liquefaction of the soil on which most of these households reside since 27F, and we can conclude that their natural capital, and that of the community at large, has been severely reduced.

5.3 Financial capital

The households from this study expressed that their limited access to financial resources seriously limits their ability to recover in an adequate and timely fashion. Having access to financial capital can, for example, enable a family to absorb the loss of their belongings or to arrange satisfactory temporary housing. For the respondents of this study, the reality was, however, that already before 27F their stock of financial capital was minimal as their situation together with others from the middle sectors was economically fragile. So in the wake of 27F, this fragility was exposed and they found themselves with no financial resources to absorb the adverse impacts and recover. The respondents of this study exposed that neither the state or any other formal organization acknowledged their financially fragile situation and subsequent limited access to financial capital for recovery. Subsequently, even in the wake of 27F they were still not eligible to receive state assistance.

Despite Chile’s extensive experience with major earthquake/tsunami event, the government did not have specific tools to be used in the wake of an earthquake/tsunami disaster. They therefore used existing mechanisms that worked in ‘normal’ situations, such as the Ficha de Proteccion Social (Social Protection Card, Chile Atiende 2015 ), to determine, for instance, a family’s level of vulnerability in light of 27F. Footnote 3 This instrument was not adapted to ensure that post-disaster needs were satisfied, however, and led to some households from ‘the middle’ with higher post-27F scores, i.e., more affluent, than before 27F (interviews Talcahuano 2013 and 2014; Chamorro et al. 2011 ). This seems unfair, to say the least, but it did determine the level and kind of assistance these households were, or were not, eligible to receive.

The ‘emerging middle’ households in Talcahuano experienced various kinds of damage. Some families with one-story dwellings and exposed to tsunamis lost practically everything, while others with two-story dwellings mainly lost belongings from their living room, dining room and kitchen, such as sofas, chairs, tables and electrical appliances (fridges, washing machines, dryers, televisions, kitchen appliances, sound equipment, etc.). While some things could be recovered with dedication and patience, most of the losses would have to be recovered over time whenever the households’ income would allow it. Since the ‘emerging middle’ households from this study had little or no financial buffers, they had to hold on to their jobs or find work as quickly as possible. This is what most of them, and in particular the men of these households, did. However, many companies in Talcahuano, like fisheries, had also been affected, so that job opportunities were scarce. Moreover, respondents revealed that some companies applied article 159 No. 6 of the Chilean Labor Code enabling them to fire workers due to a ‘fortuitous event or force majeure’ without compensation. One respondent reported that ‘They fired my husband who worked in San Vicente…interestingly enough, the company was hardly affected by the earthquake and even less by the tsunami…[but] after 2 months they took them [him and other employees] all back. As he was fired and left without any money…he was forced to leave Talcahuano and find work in the south’ (interview Talcahuano 2014). Even though some men Footnote 4 got their jobs back after a while, many households were left without an income at a time when they needed it most. Men who could not find a job in or near Talcahuano left their families behind to look for work elsewhere, which meant that many women were left in charge of most of the recovery process at home.

Because poorer households were eligible for financial assistance, there are cases where one could state that households from the ‘emerging middle’ are now worse off than those from poorer segments. I encountered several cases where this could be said. For instance, take one of my respondents from a lower segment of society. She is a Colombian single mother who came to Chile with nothing. When 27F hit, she was living with a friend in Santa Clara. She did not have a house, possessions, a job, anything. In the wake of 27F, she was able to acquire a house, goods and more importantly technical schooling to become a beautician. In other words, 27F made it possible for her to acquire a home and new skills that enabled her to earn a permanent income to ensure a livelihood. When comparing this story with those from the emergent middle households, some of whom still do not have a home 4 years after the tsunami and are still working hard to even come close to where they were before, one starts to wonder how assistance should be framed and distributed. From my study, it seems that these households are largely on their own and this could be significantly delaying their recovery. More research is necessary, however.

According to my respondents, the limited public policies directed at the emergent middle households, also in the wake of a disaster, significantly inhibited their access to financial capital and subsequently their ability to recover in a timely fashion. Their recovery often entailed finding employment to ensure an income, and over time, little by little, finding ways to set aside resources to replace what they had lost. For most, any kind of recovery required first and foremost an income to spend on daily necessities and from which to start accumulating financial resources to construct a new home (interviews 2013–2014).

Finally, the few mechanisms that were available to affected ‘middle’ households were often not responsive to their actual needs. One of my respondents explained for instance how she had only two real options to recover her house. The first option involved government assistance, but this forced the family to move from their relatively decent hill neighborhood Footnote 5 to a tsunami-affected and exposed area, and to leave behind the important social capital the family had built up over decades in their old neighborhood. In other words, receiving government assistance required giving up substantial levels of natural and social capital. The other option was to work until they could build a solid house on their land. This, however, would take a long time and forced them to continue living in the emergency accommodation until they succeeded. Since the family still owns the land on which their house is located, the ideal solution would be for the government to enable financial assistance to reconstruct a new, more solid house that can resist future earthquakes.

5.4 Political capital

For the households that I talked to, values like personal effort, sacrifice and self-sufficiency are very important. However, upholding these values seems to inhibit their access to political capital. Such values for instance discourage these households from making their grievances known and mobilizing powerful actors to address them.

These households value effort and pride themselves on achieving the life they have through hard work and sacrifice. This is why they would not become emotional at the loss of their physical house, but rather at the loss of their home ; the loss of the results of years of labor, overcoming obstacles, and the sacrifices and effort involved. It is the realization that this can be lost from one moment to the next: ‘my mother put in all the effort and sacrifice to have her house…that’s what hurts. But then I tell my mother, “that is not what matters”. We are alive. We can continue to sacrifice to have a house again. It will not be immediate because it is difficult, but at some moment we will have a house again’ (interview Talcahuano 2013). What this quotation highlights is the hurt, but also the firm belief in one’s capability to attain what one desires. From my sample, households from ‘the middle’ believe that if they put in the effort again, they will over time replace all they have lost. It might take time, blood, sweat and tears, but that’s life. This ‘effort’ ethos enables them to do what has to be done, with few complaints, but the substantial levels of acceptance also prevent them obtaining support from outside.

In addition to valuing effort, self-sufficiency is very important. My respondents from the ‘emerging middle’ would not easily ask for any kind of assistance. In particular, government assistance is perceived as ‘charity’ for ‘the needy.’ Since these households do not wish to be viewed as ‘needy’ and generally are not viewed as needy and thus do not receive much assistance, they are not keen and rather hesitant to request government assistance. While it is admirable how these households get up and start rebuilding their lives on their own, this attitude isolates them, makes them rather invisible and inhibits a speedy recovery, perhaps by mobilizing political capital. From my study, it seems that political capital is very important in Chile and can enable access to a great variety of resources. One does have to play the game, however, which entails first and foremost mobilizing the media to visibly display one’s grievances. The households I talked to have worked hard to avoid a ‘needy’ livelihood and status, so this game seems unacceptable. They would prefer a lengthy but dignified recovery process to a short and unbecoming one. Households from the ‘emerging middle’ have worked hard to not be needy, and portraying their family’s grievances for everyone to see in order to receive what they perceive as charity does not match their normative and valuative schemes. They see themselves as upwardly mobile and so do not wish to be identified with the extremely vulnerable ones that receive assistance after investing everything they have in order not to be needy.

In fact, even though the constitution (Constitución Politica de la Republica de Chile 1980 ) provides them with a right to safety and security, for instance, ‘the middle’ view such rights in a negative light, as something that is a luxury, an extra. In addition, demanding one’s rights is often considered as being rowdy and disruptive and thus does not fit their image of themselves as decent, participating citizens. Such imagery is, however, befitting the Mapuches as they struggle to see their human rights respected, for instance (interviews 2013–2014). From my time in the Greater Concepción region I learned that demanding ones rights to be respected is considered somewhat unruly and the households I engaged with preferred to stay out of trouble, accept what is and expect nothing more. In addition, as their low levels of trust in the political system also demonstrate, they do not believe that political engagement can make a difference for them. So why bother, if one is additionally too busy working to stay afloat.

Because these households largely fend for themselves and do not seek outside assistance they are rather easily ignored and generally very invisible , unlike those living in emergency camps occupying a public space, for instance. Poorer segments of society, moreover, seem increasingly to be part of the political system. Since government policies are generally pro-poor, they are part of the institutional landscape. They have direct contacts with government official and are familiar with bureaucratic processes. In addition, they are not bothered when it comes to making their grievances known through the media and seem quite capable when it comes to accessing relevant resources. This makes them visible and provides them access. In this sense, it appears that their political capital is more substantial than that of ‘the middle.’

The lack of visibility of the households that I talked to from the ‘emerging middle’ has significantly affected their access to both formal and informal relief. Since the provision of relief was not well informed, guided or coordinated, the quality and quantity of the assistance was often insufficient, but the households from ‘the middle’ would be the last to receive whatever there was because assistance would first go to wherever TV and radio journalists were reporting from. For many the media was the primary source of information. TV and radio reports largely informed the choice of location and type of assistance. This led to some areas, particularly those where people were open about their grievances, overflowing with relief and others, mostly ‘the middle’ neighborhoods, receiving very little. The neighborhood of Villamar, for instance, had been inundated by the tsunami but received no media attention, since the media was focusing on the fishing community of Tumbes and the coastal neighborhood of Santa Clara.

5.5 Social capital: ‘in life, good friends are more valuable than money’ Footnote 6

According to respondents from this study, the lack of access to different forms of capital forced them as households from ‘the middle’ to heavily rely on their informal social networks, more specifically on what Putnam ( 2000 ) labeled bonding social capital. Bonding social capital refers to forms of social capital that are inclusive, inward looking and ‘tend to reinforce exclusive identities and homogeneous groups’ (Putnam 2000 : chapter 1). Bridging social capital, on the other hand, includes forms of social capital that are more ‘outward looking and encompass people across diverse social cleavages’ (Putnam 2000 : chapter 1). It seems that households from ‘the middle’ have limited trust in people outside their direct social networks. As a result, they relied mostly on bonding social capital and turned to their extended family and informal networks to meet their needs and provide emergency accommodation, food and other resources they needed to cope with the effects of 27F. ‘Networks of reciprocity…play[ed] an important role…in creating an informal social security system to survive’ (Lomnitz 1988 : 42), as’[t]he relief; the support, came from family and friends more than from some kind of institution’ (interviews Talcahuano 2013). Because of this, neighborhoods largely populated by ‘the middle’ households did not need to stay in emergency camps or homes (mediagua); ‘many stayed with friends or family, at least for a while, until after a while such housing situations become more difficult and they are not welcome anymore’ (interviews Talcahuano 2013). Today, after 5 years, some are still living their family or friends because they have not yet been able to accumulate sufficient resources to pay for adequate accommodation. While it is great that this type of assistance gave many people a roof over their head, an emergency situation of 4 years in which two families are forced to share one small home is far from ideal.

As Lomnitz and Sheinbaum ( 2004 ) indicate, it is not surprising that in times of substantial need people turn to their extended family: Significant favors, like rebuilding a home, require a matching level of trust or ‘confianza.’ To this end, the fact that extended families in Chile include not only biological family members but also close friends and tend to be extended terms of both numbers and geographical distance is favorable. This became evident as family members and friends from far beyond the affected region organized themselves to provide assistance for those in need. In fact, these networks are global, but are mobilized to first and foremost assist members of the family. Subsequently, when 27F happened, extensive networks were activated and assistance came to Talcahuano from all over the world.

Already in 1971 did Lomnitz observe the importance of informal social networks that are largely held together by trust, for the Chilean ‘middle’ (Lomnitz and Sheinbaum 2004 : 4). She found that these networks were crucial for the Chilean middle to get access to required resources (Barozet 2006 : 23). In fact, she stressed that they were particularly valued by those who cannot seem to escape some form of social vulnerability since they enable them access to protection and security through social rather than economic capital. From this study, it became evident that this remains so. In fact, the findings corroborate that these institutions are not residues of some ‘pre-modern’ society but are important forms of capital in societies ‘where the state and market have failed to adequately insure the satisfaction of needs of all members of society’ (Lomnitz and Sheinbaum 2004 : 7). My findings support this idea for ‘the middle’: ‘the support of a social group for which [they felt] sufficient trust [and they could] rely on […] for major emergencies as well as for the satisfaction of [their] most immediate needs’ (Lomnitz and Sheinbaum 2004 : 7) was key to ‘the middle.’ Most if not all of the recovery process, whether it involved providing emergency accommodation or cleaning up debris, rested on existing informal social networks of exchange.

The need to rely on these informal social networks was exacerbated by the often unsound and unreliable functioning of the government. For instance, the failure of the tsunami warning system (Wisner et al. 2012 : chapter 26) due to prevalent inadequacies and incompetence throughout the government system led to a substantial number of unnecessary deaths and to diminished faith in the competence of state institutions. This faith was further diminished by the major delays and unreliability of government assistance due to numerous instances of fraud and bad practices. This compelled households to respond with the capital they had, i.e., social capital, to satisfy their needs.

6 Conclusion

If we go back to our approach of vulnerability, we have to conclude that a subsection of the middle-level households in Talcahuano, which we called the ‘emerging middle,’ seem more vulnerable than is generally assumed, or described in the literature. Just like anyone else in Chile they are exposed to earthquakes, but unlike most other socioeconomic segments they are also disproportionately exposed to tsunamis. And while their capacity to rebound seems high, their resilience seems to be low, and deteriorating. Their exposure is largely the result of the location of newly developed residential areas in highly exposed areas. Besides, these households have limited financial capital, i.e., opportunities to finance the cleanup and reconstruction necessary to rebound, that in light of the devastation caused by 27F has only further decreased. Finally, they command relatively low levels of political capital, which continues to be low. Fortunately for them, social capital was available to enable them to overcome the first blows, but one has to wonder to what extent they would be able to mobilize this social capital if another major adverse event were to occur. If we take this information and present it through the asset pentagons presented in Fig.  5 . Here you clearly see how their asset portfolio was already frail, but since then has deteriorated to unhealthy proportions (Fig.  7 ).

Deteriorated Asset Portfolio of the emerging middle since 27F

This study adds to research presented by the OECD, scholars like Solimano ( 2011 , 2012 ), Barozet and Fierro ( 2011 ), and Arriagada et al. ( 2012 ), identifying a vulnerable middle segment that seems to receive little or no consideration in the wake of disasters such as 27F. This ‘emerging middle’ is a rather new group that does not fit traditional middle-class frameworks. Although capturing the realities faced by this group remains difficult, this should not prevent researchers and policymakers approaching their concerns and finding ways to respond to their grievances. In ‘peacetime,’ when lives have not been disrupted by the effects of an adverse event, this group may be successful when it comes to overcoming poverty and ensuring upward mobility. But the investments necessary to do so leave these households with an extremely limited asset portfolio that does not provide the necessary buffer they need to ensure their resilience. As a result, upwardly mobile households are extremely vulnerable to unforeseen crises, stresses and shocks. In a country like Chile, where hazardous events are frequent, substantial levels of resilience are necessary. Since January 2014, for example, Chilean households have had to respond to a magnitude-8.2 earthquake/tsunami event near Iquique, devastating floods in the Atacama Desert, a disastrous fire in Chile’s primary port city Valparaiso that left thousands homeless, and three eruptions of the Chalbuco volcano.

Disasters like 27F should therefore be taken to learn more about realities faced by specific groups of vulnerable households, and the lessons learned should provide a starting point for change to increase their resilience. As the findings of this research show, increasing the resilience and reducing the vulnerability of these households does not require handouts, but rather enabling them to build up an adequate asset portfolio that will allow them to (1) reduce their exposure to risks, (2) improve their capacities to cope with unforeseen events and (3) absorb the adverse effects of events and ensure their adequate and timely recovery.

I will refer to economic fragility instead of economic vulnerability to prevent confusion regarding vulnerability.

http://gestionderiesgotalcahuano.blogspot.com/search/label/mapas , http://siit2.bcn.cl/mapoteca/mapa_view?t=Poblaci%C3%B3n%20y%20Censo&u=Comuna&s=Talcahuano&h=1 —2006 map.

The Social Protection Card (Ficha de Proteccion Social) is an instrument that is used to determine whether persons or households are entitled to state benefits. To access such benefits, the person/household should be either (socioeconomically) vulnerable or poor. To determine the socioeconomic status of the person/household at hand, a survey is used. This survey registers various aspects, such as age, education, health and income, which are later used to calculate a score and determine the person's/household's (socioeconomic) status (Chile Atiende 2015 ).

My data suggests that in Talcahuano, men are the principal breadwinners.

There is a handful of hill neighborhoods, mostly the older ones, that are decent to live in. In fact, some of these used to host the older and more affluent families of Talcahuano.

“En la vida màs vale tener amigos que dinero” is a common saying in Chile.

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Acknowledgments

I would like to express my gratitude to the Netherlands Organization for Scientific Research and the department Sociology of Development and Change of Wageningen University for believing in this study and making it financially possible. Also I would like to thank my promotor Georg Frerks, daily advisor Jeroen Warner, and my research assistant Mario Orrellana.

This study has been largely funded by the Netherlands Organization for Scientific Research, but also knows a contribution by Wageningen University.

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Assessing tsunami hazards commonly relies on historical accounts of past inundations, but such chronicles may be biased by temporal gaps due to historical circumstances. As a possible example, the lack of reports of tsunami inundation from the 1737 south-central Chile earthquake has been attributed to either civil unrest or a small tsunami due to deep fault slip below land. Here we conduct sedimentological and diatom analyses of tidal marsh sediments within the 1737 rupture area and find evidence for a locally-sourced tsunami consistent in age with this event. The evidence is a laterally-extensive sand sheet coincident with abrupt, decimetric subsidence. Coupled dislocation-tsunami models place the causative fault slip mostly offshore rather than below land. Whether associated or not with the 1737 earthquake, our findings reduce the average recurrence interval of tsunami inundation derived from historical records alone, highlighting the importance of combining geological and historical records in tsunami hazard assessment.

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Introduction.

Inadequate anticipation of the magnitude of great earthquakes in Sumatra (2004), Chile (2010) and Japan (2011) stemmed from over-reliance on short historical records that failed to account for variability in earthquake size, rupture style, tsunamigenesis and the existence of supercycles 1 , 2 , 3 . Moreover, even where long written histories exist, individual events may be missing due to failures in reporting 4 or loss of documents in times of instability or crisis (e.g. late fourteenth/sixteenth century Japan) 5 , 6 , or there may be periods where only low-quality records exist containing errors 5 . Although with other limitations, geological records are free from these problems, and it is therefore imperative that we supplement historical data with geologic records, in order to obtain robust long-term patterns to inform seismic and tsunami hazard assessments.

We show that this is the case for the area affected by the 1960 Chile earthquake (magnitude 9.5), in the 1000-km-long southernmost portion of the subduction zone formed between the Nazca and South America plates (Fig.  1 ). Besides the 1960 earthquake and other lesser events, this area experienced three great earthquakes in the historical past (since the mid-sixteenth century): in 1575, 1737, and 1837. Historical and geological evidence in the form of tsunami deposits in coastal environments 7 , 8 , 9 , 10 , 11 , 12 , and shaking-induced turbidites in lakes 13 , 14 and fjords 15 , suggest that the 1575 earthquake was similar in size and extent to that in 1960, and that both were much larger than those in 1737 and 1837. The combined evidence also suggests that large tsunamis accompanied the 1575, 1837 and 1960 earthquakes but did not in 1737. To explain the complete absence of tsunami reports in 1737 and the along-strike distribution of building damage, Cisternas et al. 16 proposed a deep interplate rupture limited to the northern half of the 1960 rupture area, and restricted to beneath land, with limited capacity for tsunami generation. However, the lack of chronicles of a tsunami could also be attributed to uprisings that had driven settlers from most of the colonial outposts in the area 9 , 16 .

Location of study area a within the regional tectonic setting and b within south-central Chile relative to sites referred to in the text and relative to rupture zones of the largest historical earthquakes. Geological evidence comes from Cisternas et al. 9 , 10 , 16 , Dura et al. 7 , Garrett et al. 11 , Hocking et al. 20 , Kempf et al. 12 , Moernaut et al. 13 , 14 and St-Onge et al. 15 ; historical evidence from Cisternas et al. 9 , 16 . Rupture lengths of historic earthquakes compiled from Cisternas et al. 16 , Dura et al. 7 and Melnick et al. 54 (dashed lines indicate where rupture extents are uncertain). Plate motions from Angermann et al. 55 . Rupture zone maps adapted from original figure drawn by Marco Cisternas.

Given the limited eyewitness reports for pre-1960 south Chilean earthquakes and tsunamis, their hypothesised rupture areas and proposed mechanisms require testing with geological evidence from coastal sites. Between the long palaeoseismic records from Tirúa 7 , 8 , 17 , 18 (38.3°S) and Maullín 9 (41.6°S), spatially there is a gap in coastal geological evidence (Fig.  1 ), in which the effects of pre-1960 events are unknown. This paper addresses this gap by presenting diatom and sedimentological evidence for historical seismic events from a tidal marsh at Chaihuín, near Valdivia, close to the region of maximum 1960 slip. We aim to (1) identify and determine the timing of multiple earthquake and tsunami events from the sedimentary record; (2) use a diatom transfer function to quantify vertical coseismic deformation; and (3) test hypotheses for pre-1960 rupture areas derived from limited historical and geological records.

Tidal observations before and after the 1960 earthquake suggest 0.7 ± 0.4 m of coseismic subsidence occurred at Chaihuín (39.95°S, 73.58°W; Fig.  2 ) in this event 19 , and sedimentological investigations confirm subsidence 20 . With respect to pre-1960 earthquakes, to date, the closest sites to Chaihuín providing geological evidence for the 1575 earthquake are ~180 km to the north (Tirúa 7 , 8 , 17 , 18 ) and south (Río Maullín 9 ), while the 1737 and 1837 events are not recorded anywhere in tidal marsh stratigraphy 9 , 11 , and their preservation in the geological record is limited to the south-central Chilean Lake District (39–40°S) 14 and coastal lowlands on Chiloé 10 . Chaihuín lies within the proposed rupture zone of the 1575 earthquake and tens of kilometres north of the proposed 1837 rupture area (Fig.  1 ). If the 1737 earthquake ruptured the northern half of the 1960 rupture area 16 , Chaihuín occupies a key location for searching for its geological signature and for delimiting the northernmost extent of the 1837 rupture. Here we present geological evidence for a previously unreported tsunami in south-central Chile, which critically reduces the average recurrence interval of tsunami inundation derived from historical records alone.

The study site is situated ~20 km southwest of Valdivia ( a ), occupying a sheltered embayment behind a large sand spit (~2 km long, ~500 m at its widest), which provides shelter from the Pacific Ocean that has promoted the development of tidal marshes and the accumulation of fine-grained sediments behind ( b ). The elevation distribution of the spit is extracted from the 1 m LiDAR Digital Terrain Model ( d ). The tidal range is low (mean higher high water [MHHW] = 0.526 m above mean sea level) and the marsh is close to the sea (<1.5 km), meaning modern diatoms should respond to tidal flooding. The sheltered location also increases the potential for preservation of evidence of seismic land-level changes and tsunami inundation. Coring locations shown on b , c —all cores (yellow dots) are presented in Aedo et al. 22 , transects X – X ’ and Y – Y ’ are presented in Fig.  3 and locations of cores analysed for diatoms marked by stars. Image sources: a Google, Landsat/Copernicus; b Google ©2021 Maxar Technologies; c , e orthomosaic and oblique drone images, authors’ own; d LiDAR data from Forestal Arauco.

Results and discussion

The chaihuín stratigraphy.

Core transects (Fig.  2b ) reveal three sand layers, intercalated between herbaceous peats, that are laterally extensive over 600 m across the marsh (Fig.  3a ). In all cases, the sand layers have sharp lower contacts and transitional upper contacts. Ten accelerator mass spectrometric (AMS) radiocarbon dates modelled using a Bayesian phased sequence model provide the chronology (Fig.  3c and Supplementary Table  1 ). The age of plant macrofossils immediately beneath the upper layer, sand A, are consistent with burial by the 1960 tsunami. The age model places the deposition of the middle sand B at 1600–1820 and lower layer, sand C, at 1486–1616 CE. The calibrated age ranges for sands B and C are reasonably broad due to plateaux in the radiocarbon calibration curve, which affect dates from the seventeenth to twentieth centuries 21 .

a Stratigraphy of selected coring transects showing three laterally extensive sand sheets. Transect locations X – X ’ and Y – Y ’ shown on Fig.  2 ; b sedimentology of sand sheets, including grain size, sorting and clastic composition (%) classified relative to six modern environments established by discriminant analysis (see  Supplementary Discussion ), with images of sands A and B in CN17/8. Box-and-whisker plots show the statistical parameters measured in sand samples with the horizontal line inside the box representing the median, the box representing the upper and lower quartiles, the whiskers representing the minimum and maximum values excluding any outliers and the crosses the extreme outlier values. The number within each box indicates the number of samples in each group; c probability density functions (95.4%) of radiocarbon dates and modelled ages for the three earthquakes. Full radiocarbon results in Supplementary Table  1 .

The sedimentology and mineralogical signatures of the sand sheets are described in detail elsewhere based on over 100 hand-driven cores 22 and summarised in Supplementary Discussion; here we analyse diatoms in three representative cores and present reconstructions of marsh surface elevation change over time from a diatom-based transfer function (Fig.  4 and Supplementary Data  1 ). From diatom analysis of the three cores, we identified 170 species indicative of differing tolerances to tidal inundation. Only 14 species were absent from a previously published modern training set that includes 29 samples from Chaihuín 20 , and 9 of these species constituted <1% of any one sample. Fallacia ny was the only species absent from the modern samples that constituted >2% of any sample (comprising 4–5% in 2 non-sand samples).

a – c Diatom assemblage summaries and dominant taxa in cores CN14/5 ( a ), CN17/8 ( b ) and CN18/11 ( c ) at elevations of 0.88, 0.89 and 1.10 m above mean sea level (MSL), respectively. Elevation optima of diatom species are classified based on weighted averaging of the modern training set and reported relative to mean higher high water (MHHW). The modern analogue technique was used to calculate the squared chord distance to the closest modern analogue, and the threshold for a fossil sample having a close modern analogue is defined as the 20th percentile of the dissimilarity values (MinDC) for the modern training set 44 . Reconstructed palaeomarsh surface elevations (PMSE) and coseismic subsidence are shown from the weighted averaging partial least squares (WA-PLS) model only. d Estimates of coseismic subsidence in 1737 from three cores and three different diatom-based transfer function approaches, showing 95.4% uncertainties.

The laterally extensive uppermost coarse to medium-grained sand sheet (A) is mid grey, varies in thickness between 1 and 19 cm, has a median grain size of 0.49 mm and is upwards fining (0.27–0.71 mm) in 61 cores (80% of those in which A is preserved, massive in the others). The marsh grades steeply into freshwater scrub, and there is no sand unit in cores just above the high marsh limit. There is an abrupt contact between the sand and dark brown silty herbaceous peat below, which contains plant material including below-ground stems (rhizomes) of Scirpus americanus . In many cores, there are rip-up clasts (~2 cm) of peat encased in the sand sheet, as well as vegetation rooted in the peat below. The peat below the sand sheet contains a diatom assemblage that is almost entirely composed of species found on the contemporary high marsh above mean higher high water (MHHW) (e.g. Eunotia praerupta , Nitzschia acidoclinata ), with higher elevation optima than the diatoms found in the herbaceous peat above the sand unit (e.g. Rhopalodia constricta ) (Fig.  4a ). The overlying peat also contains low, albeit important, percentages (5–24%) of taxa with elevation optima below MHHW. By contrast to the peats, sand A is dominated by species with lower elevation optima (59–72% of the total assemblage have optima below MHHW), including Achnanthes reversa and Planothidium delicatulum .

The middle brown-grey to dark grey mica-rich coarse to medium-grained sand sheet (B) is similarly laterally extensive across the entire marsh, varying in thickness between 2 and 32 cm. It has a median grain size of 0.47 mm and is upwards-fining (0.38–0.68 mm) in 31 cores (50% of those in which B is preserved, massive in others), but rip-up clasts of peat were only occasionally observed. In some cases, we observe a 2–4-cm-thick cap of horizontally bedded detrital plant fragments and wood at the top of the sand layer. The sand sheet abruptly overlays a red-brown to dark brown silty herbaceous peat with variable silt content and humification. Humidophila contenta dominates the diatom assemblage in the peat below sand B (up to 37% of the assemblage) and is also present in the peat overlying the sand sheet, which remains dominated by species with elevation optima above MHHW. In the core from the lowest contemporary marsh elevation (CN14/5, Fig.  4a ), there is an increase in low marsh diatom species (elevation optima below MHHW) above the sand compared to below (e.g. A. reversa , P. delicatulum ). Diatom assemblages are relatively consistent across the five samples from the sand unit, with 54–76% of the assemblages being species with elevation optima below MHHW, including A. reversa , Fallacia tenera and P. delicatulum .

A third sand deposit (C) is found in 16 cores at the southern end of the marsh, although still traceable over 200 m and across most cores that penetrated deep enough to potentially sample sand C. The deposit is a dark grey fine to medium-grained massive sand (median grain size 0.25 mm, range 0.22-0.29 mm), with a maximum thickness of 51 cm and contains occasional rip-up clasts from the buried organic unit below encased in the sand. The basal contact is abrupt, with the sand overlying a brown clayey silt with occasional herbaceous plant remains, humified organic matter and woody plant material. The organic horizon below sand C contains more diatom species typically found at lower elevations in the tidal frame than the peats below A and B (Fig.  4a ). There is also a change in species composition approaching the top of the peat, with abundances of Opephora pacifica and Pseudostaurosira perminuta decreasing and H. contenta and E. perpusilla increasing from the base to top of the peat below sand C. Also in contrast to the other two buried organic deposits, there is a change in species composition approaching the top of the peat and samples immediately above and below sand unit C have very similar diatom assemblages, dominated by H. contenta and E. perpusilla . Diatom preservation in the sand unit was very poor, and it was not possible to obtain representative counts from this unit.

Brown silty herbaceous peats separate the three sand sheets, deposited intertidally on the basis of their diatom composition. In addition to the relative variations in freshwater and brackish diatom composition of peats described above, the peat units also vary in their degree of humification. While peats below sands A and C contain humified organic matter, the peat below sand B is unhumified. Additionally, two layers of highly humified black peat were observed immediately above and below sand A in low marsh cores from the southwest of the marsh, varying in thickness between 1 and 15 cm.

Evidence for a locally sourced tsunami

We interpret all three sand sheets as being deposited by locally sourced tsunamis, rather than far-field tsunamis or non-seismic processes (e.g. storms, river floods or aeolian processes). This is based primarily on coincident land deformation, and also upon their lateral extent, diatom composition, and sedimentological signatures. Dealing first with the latter lines of reasoning, sands A and B are not only dominated by marine sublittoral and epipsammic diatom species but also contain substantial numbers of benthic silty intertidal mudflat and freshwater taxa, which also dominate the underlying peats. This is consistent with mixed diatom assemblages in tsunami deposits worldwide and indicative of tsunamis eroding, transporting and redepositing diatoms from diverse environments as they cross coastal and inland areas 23 , 24 , 25 , 26 . The presence of marine and tidal flat diatoms excludes deposition of sand by river flooding 25 , 27 , and statistical comparison of the sedimentological and mineralogical signatures of the sands with modern depositional environments, reported by Aedo et al. 22 and summarised in Supplementary Discussion, further supports a seaward rather fluvial sediment source. We observe a maximum sedimentary contribution of 12% from upstream fluvial sources (Fig.  3b ) and do not observe erosional or depositional features characteristic of fluvial flood deposits, such as a high basal mud content reflective of suspended loads during the initial stages of flooding or inverse grading as energy increases 28 .

Meteorologically driven deposition of the sands, either during storm surges or other transient sea-level fluctuation events (e.g. El Niño), is discounted as the diatoms in the overlying organic units demonstrate lasting ecological change 27 , 29 . While a non-tsunamigenic earthquake followed closely in time by a large storm surge may impact diatom assemblages in the same way, there are several further characteristics of the three sand sheets which are consistent with a tsunami origin, even though these, in themselves, are not diagnostic. These include the lateral extent (traceable across 230 m), upwards-fining grain size of sand sheets A and B, and clasts of underlying peats observed within sands A and C and occasionally within B. The absence of extreme climatic phenomena, such as hurricanes and tropical storms, in the Chaihuín area during the historic period also minimises the possibility of finding storm deposits. However, while it is recognised that the above criteria cannot be used individually to confirm tsunami deposition, it is the combination of all sedimentological and diatom evidence that we use here in support of the most compelling evidence for tsunami deposition, which comes from the accompanying abrupt land-level change. The latter rules out deposition by tsunamis sourced in the far-field, storms or aeolian processes.

Evidence for coseismic land-level change

Following established criteria 30 , 31 , we use the sedimentary and diatom evidence to propose that the Chaihuín sequence records three earthquake events, associated with vertical coseismic deformation and tsunami deposition. Diatom assemblages from immediately below sand layers A and B are characterised by species with higher elevation preferences than those found immediately above the sands, suggesting decreases in marsh surface elevation consistent with coseismic subsidence (Fig.  4 ). Diatom assemblages show minimal change across sand layer C; instead a transition occurs prior to event C whereby species with lower elevation preferences are replaced by those with higher elevation preferences, indicating net emergence prior to event C followed by minimal coseismic subsidence.

The transfer function reconstructs 0.35 ± 0.42 m of subsidence occurred in event A, which local testimony and radiocarbon dating confirm to be the 1960 earthquake. Compared to our previous estimate for this event 20 , refining the transfer function method and expanding the modern training set here, reduces the uncertainty by 0.26 m. Reconstructed subsidence agrees with observations of 0.7 ± 0.4 m 19 . By contrast, the transfer function reconstructs very minor subsidence of 0.10 ± 0.36 m occurred in event C, but this needs confirmation from analyses of additional cores.

The transfer function predicts that coseismic subsidence occurred in event B, with reconstructions varying between 0.10 ± 0.33 and 0.52 ± 0.39 m, and averaging 0.22 ± 0.38 m (Fig.  4d ). While this is close to the detection limit of coseismic land-level change 30 and the error term is large compared to the amount of deformation, we interpret event B as being associated with net submergence for two reasons. First, changes in diatom-inferred marsh elevations between pre- and post-earthquake samples are greater than other sample-to-sample changes. Second, all nine reconstructions, regardless of core location or transfer function approach, indicate submergence rather than a mixture of submergence and emergence (Fig.  4d ).

Linking the geologic and historical records

Despite the broad modelled age ranges for events B and C of 1600–1820 and 1486–1616 CE, respectively, each range only includes one historically reported earthquake. If the historical catalogue is complete, sands B and C represent tsunamis accompanying the 1737 and 1575 earthquakes, respectively. Although other great tsunamigenic earthquakes occurred in the time range of event B (1657, 1730, 1751), their rupture areas have been placed much further north 8 , 32 and therefore are very unlikely sources for the observed deformation. Age ranges do not include 1837; therefore, absence of evidence for this earthquake at Chaihuín supports the chronicle-based interpretation that the 1837 rupture area lies further south 11 , 16 . The preservation of turbidites from 1837 at sites to the north of Chaihuín 14 is consistent with observations of earthquake-triggered turbidites some distance outside the rupture zone, as observed for the M w 8.8 2010 Maule earthquake 14 .

Implications for the rupture depth in 1737

The Chaihuín record provides the first evidence for crustal deformation during the 1737 earthquake and the first evidence for the earthquake being tsunamigenic. While the nearshore bathymetry and orientation of the coastline may amplify tsunami inundation and the abundant sediment source may enhance the potential for evidence creation during even moderate tsunamis, the direction of land-level change at Chaihuín (subsidence) calls for reconsideration of the associated rupture depth. While correlation with evidence of shaking-induced turbidites from Calafquén and Riñihue lakes 14 , along with the absence of a 1737 event in sedimentary records from Río Maullín and Chucalén to the south 9 , 11 , supports the hypothesis that a smaller section of the plate interface ruptured in 1737 (between 39 and 41°S) than in 1960 and 1575 14 , the Chaihuín record also forms an important constraint on the depth of local slip in 1737.

By combining deformation and tsunami modelling, we show that our evidence of coastal subsidence and tsunami inundation at Chaihuín is better explained by offshore, shallow megathrust slip rather than by deeper slip below land as previously suggested 16 (Fig.  5 and Supplementary Fig.  1 ). This is demonstrated by a simple numerical experiment designed to find the most likely depth range of the causative earthquake rupture that can explain the coastal subsidence inferred at Chaihuín and also the tsunami inundation.

a The lower panel shows the trench-normal section of the megathrust and seafloor geometry at the latitude of Chaihuín used in the modelling experiment. The upper panel shows the bell-shaped slip distributions for a suite of eight earthquake ruptures and the middle panel shows the modelled vertical surface deformations using an elastic dislocation model (see “Methods”). The red and blue curves are the deep and shallow ruptures used as illustrative examples in the text. In this suite of models, the rupture width and peak slip are fixed at 100 km and 1 m, respectively, and the rupture location is systematically shifted horizontally in the trench-normal direction to represent ruptures at different depths. b Summary plot showing the modelled coastal uplift (left vertical axis) and tsunami runup (right vertical axis) predicted by the suite of models. Note that coastal subsidence can only be produced by offshore ruptures, with slip shallower than ~20 km. Ruptures deeper than this produce uplift at the coast. This opposing pattern of coastal deformation between shallow versus deeper ruptures is insensitive to how much slip is prescribed at the fault. Supplementary Fig.  1 shows the results for two different suite of models, in which the rupture width varies by fixing the updip (Supplementary Fig.  1a ) and downdip (Supplementary Fig.  1b ) limits.

Our numerical approach (see also “Methods”) leverages the sensitivity of the deformation sign (uplift or subsidence) and tsunami size at the Chaihuín coast to the depth of megathrust slip 33 (Fig.  5 ). An earthquake rupture with maximum slip at 33 km fault depth (Fig.  5a , red model), as previously inferred from historical records 16 , will result in coastal uplift and a relatively small tsunami. Instead, if the rupture occurs offshore (Fig.  5a , blue model), the deformation will result in coastal subsidence and a much larger tsunami. From a systematic analysis in which the hypothetical rupture models are shifted horizontally in the trench-normal direction or vertically in the depth direction (Fig.  5a , upper panel), we conclude that subsidence at the Chaihuín coast could only be produced by ruptures placed mainly offshore, at average megathrust depths shallower than 20 km (Fig.  5b , downward triangles). Deeper ruptures will produce coastal uplift and consequent smaller tsunamis (Fig.  5b ). The same conclusion is reached by varying the rupture width with fixed updip and downdip limits (Supplementary Fig.  1 ).

Our conclusions are independent of the use of a normalised unit displacement in all models (i.e. 1 m at the centre of its corresponding bell-shaped rupture) because the opposing effects of deep versus shallow ruptures at Chaihuín are insensitive to the magnitude of slip involved and depend on its locus. The amount of slip determines the magnitude of deformation but not its sign due to the elastic response of the crust during earthquakes 34 . However, with evidence at only one location we only feel confident to constrain the depth range but not the magnitude nor along-strike extent of the causative slip. Therefore, from our numerical experiment we conclude that to produce subsidence at the Chaihuín coast, an offshore rupture likely shallower than 20 km is required as a deeper source would result in coastal uplift. This is also consistent with the inferred tsunami heights (Fig.  5b ), which are larger for a shallower rupture and therefore more likely to produce inundation on land independent of the local topography. This geologically-based inference of an offshore rupture (blue curve in Fig.  5b ) contrasts with the deeper rupture below land (red curve in Fig.  5b ) previously inferred from historical observations alone 16 .

Implications for tsunami recurrence intervals

The average interval between the three events preserved at Chaihuín, 193 years, is shorter than the interval proposed for full segment 1960-style ruptures of 270-280 years 9 , 11 , 14 . This supports the notion that the Chilean subduction zone displays a variable rupture mode, in which the size, depth, tsunamigenic potential and recurrence interval vary between earthquakes 10 . Of greatest importance, however, is the shorter average recurrence interval of tsunami inundation than previously reported. With the addition of the 1737 tsunami alongside previously known events in 1960, 1837 and 1575, the historical recurrence interval for tsunamis generated anywhere along the Valdivia segment of the Chilean subduction zone is reduced to 130 years. This holds even if the inferred tsunami inundation is not associated with the 1737 earthquake, but with another earthquake of similar age missed in the historical catalogue.

Conclusions

Locally sourced tsunami deposition is the favoured mechanism for the emplacement of three sand sheets at Chaihuín tidal marsh, south-central Chile. We infer this mechanism based on the lateral extent of the deposits, sedimentological composition compared to modern environments, characteristic sedimentary structures including rip-up clasts, marine diatom assemblages that exclude a fluvial source, and most importantly, coincident abrupt marsh submergence that excludes storm surge deposition.

Tidal marsh stratigraphy and changing diatom assemblages record three episodes of abrupt land-level change accompanying the tsunami deposits. Modelled ages for the youngest and oldest deposits correspond with known tsunamigenic earthquakes in 1960 and 1575 CE. The intervening event is consistent in age with the 1737 earthquake, for which no tsunami has previously been reported. The lack of evidence for land-level change or tsunami inundation consistent with a historically documented earthquake and tsunami in 1837 confirms Chaihuín lies to the north of the 1837 rupture area.

Our identification of the first evidence for a tsunami accompanying the 1737 earthquake reveals tsunami inundation has occurred more frequently than previously thought along the Valdivia segment of the Chilean subduction zone. Furthermore, by using coupled deformation–tsunami modelling, guided by the new geological evidence, we show that the 1737 earthquake ruptured mainly offshore, at fault depths much shallower than previously proposed from historical records alone. These results provide further support for the spatiotemporal variability in ruptures within a supercycle between the 1575 and 1960 M w  > 9 earthquakes.

This study highlights that historical records may not provide complete documentation of the occurrence and characteristics of earthquakes and tsunamis occurring during the historical period. Geological evidence is essential for not only extending earthquake and tsunami histories into the past, but for verifying and supplementing historical records. This has global significance anywhere where there could be issues of absent or incomplete reporting of events, or loss of records, particularly in times of local or national crisis.

Tidal marsh sediments are excellent recorders of relative sea-level changes 35 , and in regions of palaeoseismicity, sequences of organic soils interbedded with minerogenic units often reflect vertical land-level changes that occur both coseismically during megathrust earthquakes and through intervening interseismic periods 36 , 37 . Diatoms, siliceous microfossils incorporated within these tidal marsh sediments, are used to quantify vertical land-level changes associated with great earthquakes due to the close control of salinity on their distribution in intertidal environments, as well as their high preservation potential in coastal sediments 38 . Due to their robust valves, diatoms are also widely used to determine the provenance of tsunami sediments and changing flow conditions during tsunamis 23 , 38 , 39 , 40 . In this way, diatoms have been used to reconstruct the history of earthquakes and tsunami worldwide over multi-millennial timescales 25 , 31 , 36 , 37 , 38 , providing long-term perspectives on the recurrence, magnitude and variability of earthquakes occurring along subduction zones.

Lithostratigraphy

We used marsh front exposures and 130 hand-driven gouge and Russian cores (collected between 2013 and 2018) to reveal the stratigraphy. We sought evidence for tsunami inundation in the stratigraphic record, but as sand sheets can be deposited by both seismic and a range of non-seismic sedimentary, fluvial, oceanographic or atmospheric processes, particularly storm surges 29 , 31 , we employed transects of cores (Fig.  2b ) to assess the lateral extent and continuity of sand sheets. We interpret sand sheets as being of seismic origin where these abruptly overlay organic peats in cores correlated over 10s to 100s of metres, with diatom, chronological and sedimentological analyses providing further lines of evidence 30 , 31 .

Sedimentological and mineralogical analyses

Methods used to characterise the sediments according to grain size and mineralogy are detailed in Aedo et al. 22 . To summarise briefly here, 25 subsamples (50–140 cm 3 ) were taken from the sand sheets recovered from cores to analyse the granulometry and mineralogy. Granulometric analysis followed the particle settling velocity method 41 , and central tendency and mean dispersion were calculated using GRANPLOT 42 . The mineral composition was estimated based on a modal count with a binocular microscope of 200 grains. In order to establish the origin of the sands, core sand samples were statistically compared to 22 samples taken from a series of modern environments (beach, sand bar, dunes, estuary and the outer bay, Fig.  2b ). Discriminant analysis was performed using the modern samples and four granulometric parameters (mean, selection, skewness, normalised kurtosis) as predictor variables, using the Statgraphics Centurion XVI software version 16.2.04. Finally, we also scanned selected core sections using a Geotek X-ray core imaging system at Durham University. The scanner operated at 125 kV and we used Fiji 43 to visualise the data.

Diatom analysis

A key criteria in assessment of tsunami versus non-seismic sources of sand sheets is coincident vertical land-level change 30 , 31 . We therefore analysed fossil cores for diatoms due to their well-documented utility in relative sea-level reconstruction, which is based on the relationship between species and elevation 35 . Due to varying tolerances to salinity, the frequency and duration of tidal inundation and sediment type, diatom assemblages show distinct vertical zonation across a tidal marsh. We discuss these contemporary relationships between species and marsh surface elevation in Hocking et al. 20 and use the modelled contemporary relationships to quantitatively relate the changes seen in fossil diatom assemblages to past changes in the elevation of the marsh surface via a transfer function. We prepared samples for diatom analysis following standard methods 40 and counted a minimum of 250 diatom valves per sample.

In the transfer function, we use a regional south-central Chile modern diatom training set (Supplementary Data  1 ), updated from Hocking et al. 20 . The training set consists of 148 modern samples from 6 marshes in south-central Chile (Queule, Río Lingue, Isla del Rey/Valdivia, Chaihuín, Quilo and Estero Guillingo; Fig.  1 ). We use a regional modern training set due to the superiority of the regional south-central Chile model over sub-regional and local models, both in terms of agreement with observations in 1960 and in providing fossil samples with the closest modern analogues 20 . This also follows studies elsewhere that favour regional models, particularly as the difference in age between modern and fossil samples increases and the present day marsh may no longer capture the full environmental conditions potentially present in older records 44 , 45 , 46 . While modern sample sites span ~280 km, the training set does include 29 local samples from Chaihuín, as previous studies have also highlighted the importance of including samples from the local area where possible 20 , 44 . Since publication of the modern training set in 2017, we have collected further tidal data to improve the tidal modelling and calculation of modern sample elevations, as well as updated nomenclature. These changes have resulted in a minor change in transfer function performance and required that modern tidal flat samples and those from elevations above a standardised water level index (SWLI) of 350 be excluded from the training set (see Hocking et al. 20 for explanation of standardisation of sample elevations to account for tidal range differences between sample sites). Outside of this threshold range, the transfer function does not do well at predicting elevation. The updated modern training set contains 7 samples that were not included in 2017 and excludes a further 33 samples, which were previously included.

Development of the transfer function and evaluation of transfer function performance builds upon Hocking et al. 20 . We follow the same approach of using weighted-averaging partial least squares (WA-PLS) regression (due to the unimodal nature of the diatom data) with bootstrapping cross-validation (1000 cycles), and assessed performance by using the Modern Analogue Technique to calculate the similarity between modern and fossil assemblages (reported as minimum dissimilarity coefficients). We also run a locally weighted-weighted averaging (LW-WA) transfer function model, with cross-validation and both classical and inverse deshrinking, in order to compare reconstructions derived by different transfer function methods. The three models used in the transfer function—WA-PLS (component 2), LW-WA (classical deshrinking) and LW-WA (inverse deshrinking)—have r 2 boot values between observed and predicted elevations of 0.72, 0.79 and 0.79, respectively, and root mean square error of prediction of 25.72, 22.78 and 23.42 SWLI units, respectively (equating to 0.12–0.14 m at Chaihuín).

The output of the transfer function is the palaeomarsh surface elevation (PMSE) associated with each fossil sample. To quantify coseismic deformation, we subtract the reconstructed pre-earthquake PMSE from the post-earthquake PMSE and correct for sediment accumulation, including tsunami deposition. The associated 95.4% (2 σ ) uncertainty term is the square root of the sum of the squared sample-specific standard errors for pre- and post-earthquake samples. In order to give an overall estimate of deformation for each earthquake, we average transfer function outputs from all cores and model approaches, rather than relying on a single method.

We assigned ages to sand layers by using AMS radiocarbon dating of herbaceous plant macrofossils found immediately above and below the sands. We selected above ground parts of terrestrial plants that were horizontally bedded within the sediment matrix wherever possible. Samples were analysed at high precision using multiple graphite targets, due to the potential problems for radiocarbon dating and calibrating ages from the past 400 years associated with plateaux in the radiocarbon curve 21 , 47 . We calibrated dates using the SHCal20 calibration curve 48 or the post-bomb atmospheric southern hemisphere calibration curve 49 for the samples exceeding 100% modern carbon. We report 2 σ age ranges in years CE. We used a Bayesian phased sequence model within OxCal (version 4.4) to refine the calibration solutions; this constrains the relative order and grouping of events 50 . The model includes 10 macrofossil ages; one charcoal sample was excluded due to the anomalous old age, which was out of stratigraphic order (Supplementary Table  1 ).

Rupture and tsunami modelling

We modelled coastal deformation at Chaihuín due to megathrust slip using a three-dimensional (3D) dislocation model in a uniform elastic half-space with an assumed Poisson’s ratio of 0.25. We used an extensively benchmarked computer code 51 that numerically integrates the point-source dislocation solution (Green’s function) 34 over a 3D megathrust and yields displacement values on the surface of the model. Given that we are interested in constraining the location of the rupture in the dip direction rather than in the strike direction, we constructed a megathrust that is uniform along strike and long enough to avoid 3D or edge effects. The megathrust geometry was constructed by discretizing slab data 52 at the latitude of Chaihuín into small triangular fault elements, each representing individual point-sources. Deformation at the surface was computed by the sum of the contributions from all the triangular sources. All tested earthquake rupture models consider a bell-shaped slip distribution in the dip direction with a peak slip of 1 m at its centre, which tapers updip and downdip 51 . The peak slip is fixed at unity because the sign of coastal deformation (either subsidence or uplift) depends only on the rupture depth. Constraining the slip magnitude or how it varied along-strike would require additional evidence at other sites along the south-central Chile coast. All models assume that the direction of coseismic slip (rake) is roughly 90° to represent pure dip-slip faulting.

All tsunami simulations were computed by using a finite-difference method on the actual bathymetry offshore Chaihuín. We used the well-validated numerical model COMCOT, which solves the linear shallow water equation (LSWE) and nonlinear shallow water equation using a leap-frog scheme on a staggered and nested grid system 53 . We assumed the initial sea-surface elevation to be equal to the vertical seafloor deformation due to earthquake faulting of each rupture model. The two-dimensional bathymetric profile, which we uniformly extended along strike, was constructed from global gridded bathymetric data ( www.gebco.net ), from which a two-level nested grid system was used. The first grid level with ~500 m spatial resolution was used in the source region and in deep water, where the LSWE were considered. In the coastal area of Chaihuín, we upsampled the GEBCO data by a factor of 5 to obtain a finer grid of ~100 m resolution for shallow water propagation and runup computation. Even though using a realistic, high-resolution nearshore bathymetry will change the details of the results (i.e. modelled tsunami runup values in Fig.  5b ), our simplified coarse bathymetric model is sufficient for the purpose of the numerical experiment described above. We assumed an open radiation boundary condition to the outer sea and a moving boundary on the coast. The computation time step for all grids was set to satisfy the Courant–Friedrichs–Lewy stability condition of the finite difference method. All tsunami simulations were run for 1 h, which we checked was long enough to obtain the largest runup at the coast (in this case associated with the leading wave).

Data availability

Diatom, sedimentology, stratigraphy and radiocarbon data sets are available on the Figshare repository with the identifier: https://doi.org/10.6084/m9.figshare.16617241 . Data sets used for tsunami modelling are freely available online or from linked references in the “Methods” section (COMCOT tsunami code and dislocation model 53 ; SLAB geometry 52 ; GEBCO bathymetry from www.gebco.net ). LiDAR data were donated by Forestal Arauco to the CYCLO project under a confidentiality agreement and may be obtained from the corresponding author upon reasonable request.

Code availability

The COMCOT tsunami code is available from Wang 53 and the dislocation modelling code as described in Gao et al. 51 was provided by Kelin Wang. No new computer code was written in preparing the paper.

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Acknowledgements

This research was funded by the Natural Environment Research Council (New Investigator Award NE/K000446/1), the European Union/Durham University (COFUND under the DIFeREns 2 scheme), the Millennium Scientific Initiative (ICM) of the Chilean Government (Grant Number NC160025 “Millennium Nucleus CYCLO: The Seismic Cycle Along Subduction Zones”), Chilean National Fund for Development of Science and Technology (FONDECYT grants 1190258 and 1181479) and the ANID PIA Anillo ACT192169. Radiocarbon dating support was provided by the Natural Environment Research Council Radiocarbon Facility (1707.0413, 1795.0414 and 2000.0416). LiDAR data were provided by Forestal Arauco under a collaboration agreement. We gratefully acknowledge Steve Moreton for providing the radiocarbon dates from NERC-RCF, Kelin Wang for providing the dislocation model used herein and Neil Tunstall and Chris Longley for help with core scanning. We thank Francisco Villagrán, Carlos Torres, Bill Austin, Martin Brader and Joaquim Otero for help in the field and the staff of the Valdivian coastal reserve for the facilities they provided. All sampling was undertaken with consent from the landowners; permission was acquired verbally. We thank Marco Cisternas for his insights into coastal palaeoseismology and three anonymous reviewers for their constructive comments to improve the paper. This paper forms a contribution to IGCP Projects 639 and 725.

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E.G., D.M., D.A. and E.P.H. conducted fieldwork; E.P.H. and E.G. conducted diatom analyses, developed the transfer function and developed the age model; D.A. led the sedimentological analysis; M.C. and D.M. performed the rupture and tsunami modelling; E.P.H. wrote the paper with input from all authors.

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Hocking, E.P., Garrett, E., Aedo, D. et al. Geological evidence of an unreported historical Chilean tsunami reveals more frequent inundation. Commun Earth Environ 2 , 245 (2021). https://doi.org/10.1038/s43247-021-00319-z

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Report on the 2010 Chilean earthquake and tsunami response

In July 2010, in an effort to reduce future catastrophic natural disaster losses for California, the American Red Cross coordinated and sent a delegation of 20 multidisciplinary experts on earthquake response and recovery to Chile. The primary goal was to understand how the Chilean society and relevant organizations responded to the magnitude 8.8 Maule earthquake that struck the region on February 27, 2010, as well as how an application of these lessons could better prepare California communities, response partners and state emergency partners for a comparable situation. Similarities in building codes, socioeconomic conditions, and broad extent of the strong shaking make the Chilean earthquake a very close analog to the impact of future great earthquakes on California. To withstand and recover from natural and human-caused disasters, it is essential for citizens and communities to work together to anticipate threats, limit effects, and rapidly restore functionality after a crisis.

The delegation was hosted by the Chilean Red Cross and received extensive briefings from both national and local Red Cross officials. During nine days in Chile, the delegation also met with officials at the national, regional, and local government levels. Technical briefings were received from the President’s Emergency Committee, emergency managers from ONEMI (comparable to FEMA), structural engineers, a seismologist, hospital administrators, firefighters, and the United Nations team in Chile. Cities visited include Santiago, Talca, Constitución, Concepción, Talcahuano, Tumbes, and Cauquenes. The American Red Cross Multidisciplinary Team consisted of subject matter experts, who carried out special investigations in five Teams on the (1) science and engineering findings, (2) medical services, (3) emergency services, (4) volunteer management, and (5) executive and management issues (see appendix A for a full list of participants and their titles and teams). While developing this delegation, it was clear that a multidisciplinary approach was required to properly analyze the emergency response, technical, and social components of this disaster. A diverse and knowledgeable delegation was necessary to analyze the Chilean response in a way that would be beneficial to preparedness in California, as well as improve mitigation efforts around the United States.

By most standards, the Maule earthquake was a catastrophe for Chile. The economic losses totaled $30 billion USD or 17% of the GDP of the country. Twelve million people, or ¾ of the population of the country, were in areas that felt strong shaking. Yet only 521 fatalities have been confirmed, with 56 people still missing and presumed dead in the tsunami.

The Science and Technology Team evaluated the impacts of the earthquake on built environment with implications for the United States. The fires following the earthquake were minimal in part because of the shutdown of the national electrical grid early in the shaking. Only five engineer-designed buildings were destroyed during the earthquake; however, over 350,000 housing units were destroyed. Chile has a law that holds building owners liable for the first 10 years of a building’s existence for any losses resulting from inadequate application of the building code during construction. This law was cited by many our team met with as a prime reason for the strong performance of the built environment. Overall, this earthquake demonstrated that strict building codes and standards could greatly reduce losses in even the largest earthquakes. In the immediate response to the earthquake and tsunami, first responders, emergency personnel, and search and rescue teams handled many challenges. Loss of communications was significant; many lives were lost and effective coordination to support life-sustaining efforts was gravely impacted due to a lack of inter- and intra-agency coordination.

The Health and Medical Services Team sought to understand the medical disaster response strategies and operations of Chilean agencies, including perceived or actual failures in disaster preparation that impacted the medical disaster response; post-disaster health and medical interventions to save lives and limit suffering; and the lessons learned by public health and medical personnel as a result of their experiences. Despite devastating damage to the health care and civic infrastructure, the health care response to the Chilean earthquake appeared highly successful due to several factors. Like other first responders, the medical community had the ability and resourcefulness to respond without centralized control in the early response phase. The health care community maintained patient care under austere conditions, despite many obstacles that could have prevented such care. National and international resources were rapidly mobilized to support the medical response.

The Emergency Services Team sought to collect information on all phases of emergency management (preparedness, mitigation, response, and recovery) and determine what worked well and what could be improved upon. The Chileans reported being surprised that they were not as ready for this event as they thought they were. The use of mass care sheltering was limited, given the scope of the disaster, because of the resiliency of the population. The impacts of the earthquake and the tsunami were quite different, as were the needs of urban and rural dwellers, necessitating different response activities.

The Volunteer Services Team examined the challenges faced in mobilizing a large number of volunteers to assist in the aftermath of a disaster of this scale. One of the greatest challenges expressed was difficulty in communication; the need for redundancy in communication mechanisms was cited. The flexibility and ability to work autonomously by the frontline volunteers was a significant factor in effective response. It was also important for volunteer leadership to know the emergency plans. These plans need to be flexible, include alternative options, and be completed in conjunction with local officials and other volunteers. The Executive/Red Cross Management Team took a broad look at the impacts of the earthquake and the implications for California. Some of the most important preparation for the disaster came from relationships formed before the event. The communities with strong connections between different government services generally fared well. The initial response and resilience of individuals and communities was another important component. Communication system failures limited the ability of a central government to assist impacted communities, or to issue tsunami warnings. It also delayed the response since the government did not know (in some case for several days) the impact and needs of local governments. In general, plans for congregate care shelters existed but were little used as most people chose to stay at damaged homes or with relatives. Looting was a surprise to response officials as well as social scientists, but both public and private sector organizations, including NGOs (Non-Governmental Organizations), must consider security for damaged businesses as a priority in California’s multihazard planning. Class and ethnic divisions that become heightened during some cases of actual or perceived injustice may also emerge in natural disasters in California.

Several factors contributed overall to the low casualty rate and rapid recovery. A major factor is the strong building code in Chile and its comprehensive enforcement. In particular, Chile has a law that holds building owners accountable for losses in a building they build for 10 years. A second factor was the limited number of fires after the earthquake. In the last few California earthquakes, 60% of the fires were started by electrical problems, so the rarity of fires may have been affected by the shut down of the electricity grid early in the earthquake. Third, in many areas, the local emergency response was very effective. The most effective regions had close coordination between emergency management, fire, and police and were empowered to respond without communication with the capital. The fourth factor was the overall high level of knowledge about earthquakes and tsunamis by much of the population that helped them respond more appropriately after the event.

Citation Information

Publication Year	2011
Title	Report on the 2010 Chilean earthquake and tsunami response
DOI
Authors
Publication Type	Report
Publication Subtype	USGS Numbered Series
Series Title	Open-File Report
Series Number	2011-1053
Index ID
Record Source
USGS Organization	Multi-Hazard Demonstration Project

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Earthquake had surprising ecological effects in Chile

Yet that’s exactly what researchers found in a study of the sandy beaches of south central Chile, after an 8.8-magnitude earthquake and devastating tsunami in 2010.

Their study also revealed a preview of the problems wrought by sea level rise–a major symptom of climate change.

In a scientific first, researchers from Southern University of Chile and the University of California, Santa Barbara (UCSB) were able to document the before-and-after ecological impacts of such cataclysmic occurrences.

A paper appearing today in the journal PLoS ONE details the surprising results of their study, pointing to the potential effects of natural disasters on sandy beaches worldwide.

The study is said to be the first-ever quantification of earthquake and tsunami effects on sandy beach ecosystems along a tectonically active coastal zone.

“So often you think of earthquakes as causing total devastation, and adding a tsunami on top of that is a major catastrophe for coastal ecosystems,” said Jenny Dugan, a biologist at UCSB.

“As expected, we saw high mortality of intertidal life on beaches and rocky shores, but the ecological recovery at some of our sandy beach sites was remarkable.

“Plants are coming back in places where there haven’t been plants, as far as we know, for a very long time. The earthquake created sandy beach habitat where it had been lost. This is not the initial ecological response you might expect from a major earthquake and tsunami.”

Their findings owe a debt to serendipity.

The researchers were knee-deep in a study supported by FONDECYT in Chile and the U.S. National Science Foundation’s (NSF) Santa Barbara Coastal Long-Term Ecological Research (LTER) site of how sandy beaches in Santa Barbara and south central Chile respond, ecologically, to man-made armoring such as seawalls and rocky revetments.

By late January, 2010, they had surveyed nine beaches in Chile.

The earthquake hit in February.

Recognizing a unique opportunity, the scientists changed gears and within days were back on the beaches to reassess their study sites in the catastrophe’s aftermath.

They’ve returned many times since, documenting the ecological recovery and long-term effects of the earthquake and tsunami on these coastlines, in both natural and human-altered settings.

“It was fortunate that these scientists had a research program in the right place–and at the right time–to allow them to determine the responses of coastal species to natural catastrophic events,” said David Garrison, program director for NSF’s coastal and ocean LTER sites.

The magnitude and direction of land-level change resulting from the earthquake and exacerbated by the tsunami brought great effects, namely the drowning, widening and flattening of beaches.

The drowned beach areas suffered mortality of intertidal life; the widened beaches quickly saw the return of biota that had vanished due to the effects of coastal armoring.

“With the study in California and Chile, we knew that building coastal defense structures, such as seawalls, decreases beach area, and that a seawall results in the decline of intertidal diversity,” said lead paper author Eduardo Jaramillo of the Universidad Austral de Chile.

“But after the earthquake, where significant continental uplift occurred, the beach area that had been lost due to coastal armoring has now been restored,” said Jaramillo. “And the re-colonization of the mobile beach fauna was underway just weeks afterward.”

The findings show that the interactions of extreme events with armored beaches can produce surprising ecological outcomes. They also suggest that landscape alteration, including armoring, can leave lasting footprints in coastal ecosystems.

“When someone builds a seawall, beach habitat is covered up with the wall itself, and over time sand is lost in front of the wall until the beach eventually drowns,” said Dugan.

“The semi-dry and damp sand zones of the upper and mid-intertidal are lost first, leaving only the wet lower beach zones. This causes the beach to lose diversity, including birds, and to lose ecological function.”

Sandy beaches represent about 80 percent of the open coastlines globally, said Jaramillo.

“Beaches are very good barriers against sea level rise. They’re important for recreation–and for conservation.”

Republished with permission from the National Science Foundation .

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Maule, 2010 Chile Earthquake and Tsunami

The 2010 Chile earthquake occurred off the Maule coast of central Chile on Saturday, 27 February 2010, at 03:34 local time, having a magnitude of 8.8 on the moment magnitude scale, with intense shaking lasting for nearly four minutes. It occurred on the subduction zone plate boundary at the Peru - Chile Trench where the oceanic Nazca Plate subducts beneath the continental South American Plate. The two plates are converging at a rate of 80 mm per year. The epicentre was just 70 miles (115 kilometres) from Concepcion, Chile's second-largest city.

The 2010 Chile earthquake ranks as the sixth largest earthquake ever to be recorded by a seismograph. It was the most powerful tremor to hit Chile in 50 years. It was felt strongly in six Chilean regions (from Valparaiso in the north to Araucania in the south), that together make up about 80 percent of the country's population. According to the United States Geological Survey (USGS), the cities experiencing the strongest shaking at grade VIII (Destructive) on the Mercalli intensity scale (MM) were Arauco and Coronel. According to Chile's Seismological Service, Concepcion experienced the strongest shaking at MM IX (Violent).

The earthquake was felt in the capital Santiago at MM VII (Very Strong) and MM VIII (Destructive).

Tremors were felt in many Argentine cities, including Buenos Aires, Cordoba, Mendoza and La Rioja. Tremors were felt as far north as the city of Ica in southern Peru (approx. 2400 km).

The tsunami waves that followed this event affected the coastal regions between the cities of Valparaiso and Valdivia, with minor effects as far as Coquimbo. The tsunami devastated several coastal towns from Tirua to Pichilemu (spanning over 500 Km.) and damaged the port at Talcahuano.

According to field observations tsunami heights reached ca. 14 m in the coastal area of the Maule region immediately north of the epicentre, and diminished progressively northwards to 4-2 m near Valparaiso. Along the coast of Cobquecura, tsunami height values were inferior to 2-4 m.

More variable tsunami heights of 6-8 m were measured at Dichato-Talcahuano and Tirua-Puerto Saavedra, in the Bio Bio and Arauco regions, respectively, to the south of the epicentre. According to eyewitnesses, the tsunami reached the coast between 12 to 20 and 30 to 45 minutes in areas located closer and faraway from the earthquake rupture zone, respectively.

Destructive tsunami waves arrived also between 2.5 and 4.5 hours after the main shock, especially along the coast of the Bio Bio and Arauco regions. The tsunami effects were highly variable along the coast, as a result of geomorphological and bathy-metric local conditions, besides potential complexities induced by the main shock.

The earthquake-triggered tsunami radiated across the Pacific basin and swamped Chile's sparsely inhabited Juan Fernandez Islands, the island chain that inspired the story of Robinson Crusoe, killing at least 8 people.

Tsunami warnings were issued in 53 countries, and the wave caused minor damage in the San Diego area of California and in the Tohoku region of Japan, where damage to the fisheries business was estimated at Yen 6.26 billion (US $66.7 million).

Steve Wollf, the author of this video, says: "San Diego was the first point in the US to be subjected to the tsunami (hence it would receive the largest waves). A friend of mine visiting from out of town decided to brave the storm and check it out. We were doubtful that we'd see anything at all, but decided to head to Point Loma, a spit of land that extends furthest out into the ocean and overlooks San Diego. From our comfortable and scenic perch about 300ft above sea level, this video shows what we saw before and during the tsunami. We later checked the times with the ranger station, so what we saw coincided time-wise with the tsunami event. Fortunately, San Diego was spared. My commiserations to the victims of this latest earthquake in Chile."

In Chile 525 people lost their lives, 25 people went missing and about 9% of the population in the affected regions lost their homes. According to Ministry of Interior data in May 2010, 124 of the 550 identified casualties and missing were attributed to the tsunami.

On 10 March, Swiss Reinsurance Co. estimated that the Chilean quake and tsunami would cost the insurance industry between 4 and 7 billion dollars. The rival German-based Munich Re AG made the same estimate. Earthquake's losses to economy of Chile are estimated at US $15-30 billion.

Did you know that..

The 2010 Chile earthquake and tsunami destroyed over 81,000 houses, and another 109,000 were severely damaged.

The earthquake generated a blackout in Chile that affected 93 percent of the country's population and which went on for several days in some locations. Restoring power in many cities in the immediate aftermath was impossible because of damage from the tsunami.

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The 2010 tsunami in Chile: Devastation and survival of coastal small-scale fishing communities

2010, Marine Policy

Related Papers

Geosciences

Carlota Cubelos

The Sendai Framework for Disaster Risk Reduction emphasizes the need to rebuild better after a disaster to ensure that the at-risk communities can withstand a similar or stronger shock in the future. In the present work, the authors analyzed the reconstruction paths through a comparative analysis of the perspective of a community in Japan and another in Chile, and their respective local governments. While both countries are at risk to tsunamis, they follow different reconstruction philosophies. Data was gathered through key informant interviews of community members and local government officials, by adapting and modifying the Building Resilience to Adapt to Climate Extremes and Disasters (BRACED) 3As framework to a tsunami scenario. The 3As represent anticipatory, adaptive, and absorptive capacities as well as transformative capacities and respondents were asked to rate this according to their perspectives. It was found that while both communities perceive that much is to be done in recovery, Kirikiri has a more holistic and similar perspective of the recovery with their government officials as compared to Dichato. This shows that community reconstruction and recovery from a disaster requires a holistic participation and understanding.

Miguel Angel Cabrera

In this chapter, we present a case study from Yucatan, Mexico. The main hazards that fisher groups are confronted with in coastal areas are explored, as well as the coping strategies fishers have developed to face them. We also investigate the sense of well-being according to fishers’ perceptions, and contrast with the level of marginalization reported in official records. Our findings suggest that fishers do not consider themselves poor, as long as they have access to fishing. Fishing gives them food security, but declining catches and other factors beyond their control, such as increase in the frequency of hurricanes and red tides, also expose them to risk and vulnerability. Several social and political issues generate concern among fishers as well. They employ proactive and reactive strategies at the individual and community levels to face those challenges. However, our research discovered that there are differences between communities and groups of fishers regarding those strategies. We contend that socio-economic conditions and levels of organization influence the ways fishers develop coping strategies. We discuss our findings in light of strategies that can be promoted to improve adaptive capacity of fishers in coastal communities, averting them from vulnerable conditions.

International Journal of Disaster Risk Reduction

Ricardo San Carlos Arce

researchgate.net

Zulhamsyah Imran

IOSR Journals

Florence Poulain

Karen Engel

Nurulhuda Ahmad Fatan

Procedia Environmental Sciences

Miguel Esteban

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The generation of new tsunami risk areas due to an intentionally biased reconstruction process: Case study of llico after the 2010 Chile tsunami

The main objective of the present work is to assess changes in vulnerability and, consequently, risk, considering a time-space dimension. Three deterministic tsunami scenarios based on historical events were analyzed, and vulnerability analysis with an emphasis on social cohesion and community organization in pre-reconstruction (2012) and post-reconstruction (2017) conditions was carried out using physical, socioeconomic and social organization variables.

The extreme scenario was found to be a 2010-like tsunami, and high levels of social trust and community cooperation were found in pre-reconstruction conditions, which decreased in post-reconstruction conditions due to the relocation of the affected population to other parts of the region.

Therefore, it can be concluded that even though physical aspects are important for improving the livability of an affected place and the quality of life of its inhabitants, intentionally biased reconstruction processes (focused mainly on physical aspects) do not effectively reduce risk. Finally, it is extremely important to include social capital and social resilience as crucial elements in public policies to implement more comprehensive and successful reconstruction processes in developing countries that may be affected by many natural hazards such as earthquakes, tsunamis, river floods, volcanic eruptions and storm surges.

Document links last validated on: 16 July 2021

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Chile 2010 Tsunami Case Study

Subject: Geography

Age range: 16+

Resource type: Assessment and revision

Last updated

30 December 2016

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