Chile Earthquake Research Articles

Back to full interseismic plate locking decades after the giant 1960 Chile earthquake

Great megathrust earthquakes arise from the sudden release of energy accumulated during centuries of interseismic plate convergence. The moment deficit (energy available for future earthquakes) is commonly inferred by integrating the rate of interseismic plate locking over the time since the previous great earthquake. But accurate integration requires knowledge of how interseismic plate locking changes decades after earthquakes, measurements not available for most great earthquakes. Here we reconstruct the post-earthquake history of plate locking at Guafo Island, above the seismogenic zone of the giant 1960 (Mw = 9.5) Chile earthquake, through forward modeling of land-level changes inferred from aerial imagery (since 1974) and measured by GPS (since 1994). We find that interseismic locking increased to ~70% in the decade following the 1960 earthquake and then gradually to 100% by 2005. Our findings illustrate the transient evolution of plate locking in Chile, and suggest a similarly complex evolution elsewhere, with implications for the time- and magnitude-dependent probability of future events.

Prenatal Exposure to an Acute Stressor and Children's Cognitive Outcomes.

Exposure to environmental stressors is highly prevalent and unequally distributed along socioeconomic lines and may have enduring negative consequences, even when experienced before birth. Yet, estimating the consequences of prenatal stress on children's outcomes is complicated by the issue of confounding (i.e., unobserved factors correlated with stress exposure and with children's outcomes). I combine a natural experiment-a strong earthquake in Chile-with a panel survey to capture the effect of prenatal exposure on acute stress and children's cognitive ability. I find that stress exposure in early pregnancy has no effect on children's cognition among middle-class families, but it has a strong negative influence among disadvantaged families. I then examine possible pathways accounting for the socioeconomic stratification in the effect of stress, including differential exposure across socioeconomic status, differential sensitivity, and parental responses. Findings suggest that the interaction between prenatal exposures and socioeconomic advantage provides a powerful mechanism for the intergenerational transmission of disadvantage.

Low-parametric modeling of the 2015, MW 8.3 Illapel, Chile earthquake

The MW 8.3 (GCMT) Illapel megathrust earthquake is investigated. The objective is to find out which features of the previously published rupture scenarios can be resolved by using a regional strong-motion network (epicentral distances 130–260 km) and source models with a few parameters only. Low-frequency waveforms (<0.05 Hz) at nine stations (Centro Sismológico Nacional, Chile) are subjected to modeling. Various representations of the source are used: (i) multiple-point source models based either on iterative deconvolution or simultaneous inversion of source pairs, (ii) models of circular and elliptical uniform-slip patches, employing synthetic and empirical Green's functions, respectively. This variety of methods provides consistent results. The earthquake appears to be a segmented rupture progressing from an early (deep) moment release to a later (shallow) one, towards the northwest. The source models of slip-uniform patches synchronously suggest a low rupture speed of 1–2 km/s. Despite the different data sets and methods used in this study, the estimate of rupture speed is consistent with independent publications. As for ambiguity in literature regarding the depth and timing of the rupture, our paper clearly prefers the models including a ∼20–30 s delay of the shallow moment release compared to the initial deep one. The strong-motion data set and low-parametric models proved to be competitive with more sophisticated approaches like multi-parameter slip models using a variety of regional geophysical observables. These results, together with the results from other studies for smaller events, show that strong-motion networks can be useful for studying rupture processes in a wide range of magnitudes, thus promoting the improvement of regional strong-motion networks in poorly instrumented regions.

Seismo-Ionospheric Variations during Strong Earthquakes Based on the Example of the 2010 Earthquake in Chile

Seismo-ionospheric variations during the strong earthquake on February 27, 2010 in Chile have been considered. An analysis of the ionospheric state has been performed using measurements based on a GPS satellite navigation system. The results of processing have shown that the decrease in the electron concentration on February 24, 2010 relative to the preceding day was from 24 to 35%. It has also been noted that, 3 days prior to the seismic event, a substantial drop in the rate of change of in the total electron content was observed near the epicenter zone for 1.5 h. It has been shown that, directly before the earthquake, instantaneous variations in the rate of change in the electron content by an order of value that exceeds normal background behavior was observed.

Reply to the comment on “Historical and recent large megathrust earthquakes in Chile”

Reply to the comment on “Historical and recent large megathrust earthquakes in Chile”

Communal coping and rumination in the aftermath of Chile earthquake: Multiple mediation analysis of the relationship between subjective severity and posttraumatic growth

AbstractCommunal coping and collective participation were recently proposed as a potential mechanism that may favour not only individual's capacity to bounce back but also community cohesion and social well‐being and posttraumatic growth in the aftermath of natural disasters. To date, there is a lack of studies simultaneously assessing the effect of communal coping strategies and cognitive strategies on the development of posttraumatic growth. Therefore, the aim of this study was to examine the role of communal coping strategies and cognitive strategies such as intrusive and deliberated rumination as potential mediators between subjective severity of the event and posttraumatic growth and positive adjustment in the context of natural disaster. The questionnaire was administrated to 225 people affected by the most intense earthquake recorded in Chile in this century. The results of multiple mediation analysis showed that both cognitive strategies, such as deliberative rumination, and communal coping strategies, such as communal positive reappraisal and participation in spiritual rituals, are potential mediators between subjective severity and posttraumatic growth. Overall, the present work offers researchers and professionals interested in this area of study an interesting approach to analyse individual and collective coping strategies and its interrelation.

Comment on “Historical and recent large megathrust earthquakes in Chile” by Ruiz and Madariaga, 2018

Comment on “Historical and recent large megathrust earthquakes in Chile” by Ruiz and Madariaga, 2018

The variometric approach to real-time high-frequency geodesy

High-frequency geodesy is here intended as the capability of retrieving information relevant to geodesy and geophysics at high frequency through geodetic measurements and methodologies. In particular, this short review work focuses on two aspects: fast ground motions, as those due to earthquakes, and fast ionospheric total electron content (TEC) disturbances, as those caused by tsunamis. This information can be retrieved, even in real time, from Global Navigation Satellite System observations collected at high rate (equal or higher than 1 Hz), and can significantly support geohazard understanding contributing in seismic moment estimation and tsunami early warning. Here, the real-time possibilities of the new variometric approach for high-frequency geodesy are summarized: the fundamental idea is to directly focus on the quantities of interest, which are “variations” (of positions, of ionospheric TEC) and can be properly estimated in real time. The work moves “from ground to ionosphere”: with respect to the ground, the more consolidated application of the variometric approach to GNSS seismology (VADASE) is presented, up to the latest developments; with respect to the ionosphere, the brand new application named VARION for TEC disturbances computation is described, and the first results of the application to the Illapel, Chile earthquake (USGS $$M=8.3$$ , 16 September 2015, 22:54:32 UTC) are shown.

GPS/GLONASS Combined Precise Point Positioning With the Modeling of Highly Stable Receiver Clock in the Application of Monitoring Active Seismic Deformation

AbstractThe high‐rate kinematic Precise Point Positioning (PPP) of the Global Navigation Satellite System has become an effective method for monitoring crustal deformation caused by earthquakes. In this contribution, the method of GPS/GLONASS PPP with the receiver clock modeling is applied in active seismic deformation monitoring for the first time. With the modeling method, the short‐term vertical positioning accuracy of 2–4 mm that usually cannot be obtained by standard PPP is achieved. Our PPP results confirm that the positioning accuracy is improved due to the increase of GLONASS observations compared to the GPS‐only solution. Based on the external seismic data and the high‐rate GPS/GLONASS data for the 2011 Japan earthquake and 2010 and 2015 Chile earthquakes, comparative analyses concerning receiver clock modeling are carried out. The results show that a high degree of decorrelation between the height position estimates and receiver clock offsets can be obtained by using the receiver clock modeling. The short‐term accuracy of the GPS‐based vertical displacements is improved to the level of about 4.4 mm, and the short‐term accuracy of better than 4 mm for the GPS/GLONASS‐combined vertical displacements is achievable. Furthermore, the weak vertical signals that are not detected by standard PPP can be captured with the modeling of highly stable receiver clock.

Gentrification in (re)construction: Talca’s neighbourhoods post 2010 earthquake

PurposeThis study aims to explore the complex relationship between post-earthquake reconstruction processes and gentrification in neighbourhoods of intermediate cities, calling on the critical role of recovery strategies in altering neighbourhoods physical and social urban structure identities.Design/methodology/approachThe paper uses a case study; the reconstruction process of the neighbourhoods post-2010 earthquake in Talca, Chile, and analyses in a six-year timeline its socio-spatial changes. The latter based on mixed methods, primary data from strategic interviews with key stakeholders, cadastres of land value and real estate housing projects and neighbourhood polls, and secondary data from official documents such as plans and policies.FindingsThe findings suggest that patterns of incipient gentrification are an outcome of the reconstruction strategies. Acknowledging the intricate interplay amongst urban neoliberal conditions, historical heritage and identities and post-disaster recovery, inadequate housing subsidies and normative plans are causing the displacement of hundreds of historical residents and resistance, arrival of newcomers with higher debt capacity in new housing typologies and increasing land value. Process related to neoliberal politics of state led to new-build gentrification.Originality/valueGentrification and reconstruction are both processes that modify urban structures, society and perceptions, and yet their socio spatial effects have never been studied in a cumulative and integrated manner, even more, in intermediate cities. The value is to rethink the critical role of recovery strategies in halting and containing gentrification in fast transforming secondary cities.

Chilean megathrust earthquake recurrence linked to frictional contrast at depth

Fundamental processes of the seismic cycle in subduction zones, including those controlling the recurrence and size of great earthquakes, are still poorly understood. Here, by studying the 2016 earthquake in southern Chile—the first large event within the rupture zone of the 1960 earthquake (moment magnitude (Mw) = 9.5)—we show that the frictional zonation of the plate interface fault at depth mechanically controls the timing of more frequent, moderate-size deep events (Mw 8.5). We model the evolution of stress build-up for a seismogenic zone with heterogeneous friction to examine the link between the 2016 and 1960 earthquakes. Our results suggest that the deeper segments of the seismogenic megathrust are weaker and interseismically loaded by a more strongly coupled, shallower asperity. Deeper segments fail earlier (~60 yr recurrence), producing moderate-size events that precede the failure of the shallower region, which fails in a great earthquake (recurrence >110 yr). We interpret the contrasting frictional strength and lag time between deeper and shallower earthquakes to be controlled by variations in pore fluid pressure. Our integrated analysis strengthens understanding of the mechanics and timing of great megathrust earthquakes, and therefore could aid in the seismic hazard assessment of other subduction zones. The recurrence time of megathrust earthquakes in Chile may be controlled by frictional contrasts at depth, according to analyses of stress build-up and release related to the December 2016 southern Chile earthquake.

Effect of long-duration earthquakes on the low-cycle fatigue damage in RC frame buildings

Several cases of failure due to rupture of reinforcing bars in RC buildings were reported by inspection teams after the 2010 Muale earthquake in Chile that triggered further research efforts.This paper studies the effect of long-duration earthquakes on the damage potential due to low-cycle fatigue through nonlinear analysis of three existing RC frame buildings. The number of strain cycles and their amplitudes for reinforcing bars at the critical locations within each building were obtained from nonlinear time history analyses. The reduction in the fatigue life has been estimated using S-N curve obtained from the experimental literature and by applying the Palmgren-Miner damage rule.The results showed significant reduction in fatigue life for the low- and medium-rise buildings larger than high-rise buildings. It was found that A706 steel has longer fatigue life than A615 steel. Also, larger diameter steel bars tend to experience less fatigue damage within RC members.

An Integrated Methodology for Displacement-Based Seismic Design of Homogeneous Slopes

This paper presents an integrated methodology for displacement-based seismic design of homogeneous slopes under typical surcharge loading and slope inclination conditions. Charts developed over the basis of dimensionless parameters are given for both selection of the static safety factor of the slope and determination of the corresponding critical pseudo-static acceleration coefficient in the seismic case. In addition, graphs based on the well-known Newmark's sliding block method are proposed for estimation of slope displacements as a function of the critical seismic coefficient. For this purpose, a series of strong ground motion records from two major Chilean earthquakes grouped by soil conditions were utilized. In this way, a simple and rational design procedure can be followed in order to integrate the desired static safety factor of the slope, the amount of seismic displacement judged to be allowable, and the minimum stability requirements for the slope in the seismic case. The proposed methodology can be used in both preliminary calculations and rapid engineering analyses of homogeneous slopes located at sites with similar seismic characteristics to the Chilean subduction zone.

Women\u2019s empowerment following disaster: a longitudinal study of social change

This paper examines changes in gender relations in a small coastal community as a result of the 2010 Chile earthquake and tsunami. Vulnerability and resilience are used as a conceptual framework to analyse these changes. Based on empirical evidence from a seven-year longitudinal study and quasi-ethnographic work, we explore changes in power relations at the different stages of the disaster and longer-term recovery as well as the conditions that fostered these changes. Our findings show distinct patterns of change. First, disasters can trigger long-lasting changes that challenge historical patriarchal relations. Second, while vulnerability increases following a disaster, resilience can potentially counteract women’s vulnerability. We propose that resilience can be a pathway to produce long-term changes in gender relations and empower women in the context of disasters.

G‐FAST Earthquake Early Warning Potential for Great Earthquakes in Chile

G‐FAST Earthquake Early Warning Potential for Great Earthquakes in Chile

Reprint of 'Unusual geologic evidence of coeval seismic shaking and tsunamis shows variability in earthquake size and recurrence in the area of the giant 1960 Chile earthquake'

An uncommon coastal sedimentary record combines evidence for seismic shaking and coincident tsunami inundation since AD 1000 in the region of the largest earthquake recorded instrumentally: the giant 1960 southern Chile earthquake (Mw 9.5). The record reveals significant variability in the size and recurrence of megathrust earthquakes and ensuing tsunamis along this part of the Nazca-South American plate boundary. A 500-m long coastal outcrop on Isla Chiloé, midway along the 1960 rupture, provides continuous exposure of soil horizons buried locally by debris-flow diamicts and extensively by tsunami sand sheets. The diamicts flattened plants that yield geologically precise ages to correlate with well-dated evidence elsewhere. The 1960 event was preceded by three earthquakes that probably resembled it in their effects, in AD 898–1128, 1300–1398 and 1575, and by five relatively smaller intervening earthquakes. Earthquakes and tsunamis recurred exceptionally often between AD 1300 and 1575. Their average recurrence interval of 85years only slightly exceeds the time already elapsed since 1960. This inference is of serious concern because no earthquake has been anticipated in the region so soon after the 1960 event, and current plate locking suggests that some segments of the boundary are already capable of producing large earthquakes. This long-term earthquake and tsunami history of one of the world's most seismically active subduction zones provides an example of variable rupture mode, in which earthquake size and recurrence interval vary from one earthquake to the next.

Repercussions of the Great East Japan Earthquake tsunami on ellipsoidal Alexandrium cysts (Dinophyceae) in Ofunato Bay, Japan

Shellfish aquaculture in Ofunato Bay, Northeast Japan, was seriously damaged by a tsunami generated by the Great East Japan Earthquake, March 11th, 2011, accompanied by paralytic shellfish poisoning (PSP) outbreaks caused by Alexandrium tamarense (Dinophyceae). To understand longer future trends of PSP, an investigation was made of the historical occurrence and causes of Alexandrium outbreaks after the tsunami. Vertical distributions of Alexandrium cysts in two sediment-cores from Ofunato Bay revealed that the sediments above ca. 25 cm were eroded, re-suspended and re-deposited, and they included unusually abundant Alexandrium cysts. This abundance of cysts was due to re-deposition of older sediments by the tsunami. The first Ofunato Bay PSP incident was in 1961 after the Chilean Earthquake tsunami and was probably caused by similar unusual blooms of Alexandrium germinated from older sediments as the Great East Japan tsunami, together with nutrient enrichment because of population increase at the start of shellfish aquaculture.

The Confirmed Cosmic Energy Gravitational Genesis of the Strongest Japanese, Italian, Greek, Chinese and Chilean Earthquakes

The Confirmed Cosmic Energy Gravitational Genesis of the Strongest Japanese, Italian, Greek, Chinese and Chilean Earthquakes

The role of communities in coping with natural disasters: Lessons from the 2010 Chile Earthquake and Tsunami

This paper examines the impact of the 2010 Chile earthquake and tsunami on community resilience, and the crucial role that communities had to play in coping with this event. The results of a primary research conducted in Talcahuano, one of the worst affected cities by the disaster (through methods of semi-structured interviews, observation, documentary review and social media) show that communities have the power to activate internal resilience capacities to cope with and recover from natural disasters. For instance, the role of social networks, organisation, cooperation, trust, local knowledge, and participation was crucial at all stages of the disaster. The study highlights that communities are not simply passive victims of disasters; rather, they are active agents. The lessons from the 2010 Chile earthquake and tsunami can become a useful operational tool for managing efficiently emergency situations in vulnerable communities and planning effective and sustainable disaster risk reduction policies in developing countries.

Improved Risk Assessment of Tsunami Inundation Based on Geospatial and Local Knowledge for Sustainable Development

Tsunami events have extensive implications for sustainable development, due to the social, economic, and environmental impacts they can cause. Take into account the competence of geospatial and local knowledge; these sources are integrated to assess tsunami risk assessment by utilizing satellite imageries. The study area of Talcahuano experienced severe damages due to the 2010 Chile earthquake and tsunami. The geospatial information of the damaged areas was identified by processing the surface reflectance values between pre- and post-disaster images of the satellite optical and SAR data. The DEM data was also employed to delineate areas according to the inundation height data. Local information of tsunami inundation was generated through a DIG participatory mapping. Both types of inundation maps showed good agreement with the results of field surveys. Furthermore, a map of the potential tsunamiinundation zone was produced to aid integrated risk assessments in the area. The map showed areas with high, medium, and low inundation level adopted from the satellite images and the DIG map. Keywords: Tsunami Inundati Satellite Imageries, Optical and SAR Sensor, DIG, Disaster Risk Reduction