Peru Earthquake Research Articles

Estimation of the Seismic Source of the 1974 Lima Peru Earthquake and Tsunami (Mw 8.1)

In this investigation, we have conducted a long period teleseismic and tsunami waveform inversion to obtain the slip distribution of the 1974 Lima-Perú earthquake occurred in the central region of Peru. According to teleseismic inversion, the rupture process was complex with a duration of 90 s approximately and the main asperity was located in the northern side of the rupture geometry, offshore Lima and Callao. According to tsunami waveform inversion the main asperity was located in the southern side of the fault plane, offshore Cañete. However, a joint inversion of teleseismic and tsunami waveforms averaged the contribution of the two datasets and could give a better result. The maximum slip from the joint inversion was 7.25 m, and the moment magnitude was Mw 8.1. Despite the occurrence of this earthquake (almost 50 years ago), there is a high seismic potential to trigger a tsunamigenic earthquake in the central region of Peru. According to the interseismic coupling the next earthquake in the central region of Peru is ready to occur and it would be of 8.5–8.8 Mw.

Seismicity Based Maximum Magnitude Estimation of Subduction Earthquakes in Peru

In seismic design, intensity parameters that represent seismic demand are commonly used. A probabilistic seismic hazard assessment is an accurate way of assessing seismic demand, based on a set of parameters that represent the seismicity of a region. However, because some regions lack sufficient information, the selection of these parameters can be controversial. In Peru, selecting a maximum earthquake magnitude (Mmax) for regional seismic hazard assessments has proven to be a challenging task due to the limited available information concerning of large-magnitude events. This study evaluated the Mmax for subduction earthquakes using scaling relationships, empirical evidence, and the extreme value statistics (Kijko and Bayesian) approach. The seismic catalog was updated to February 2022 and divided into 19 subduction seismic sources (5 interface and 14 intraslab). The results showed that the obtained Mmax are within the range of Mw 8.7–9.0 for the interface and Mw 7.6–8.1 for the intraslab sources, which unlike the Mmax values established in previous regional seismic hazard assessments, are more consistent with the historical and instrumental seismicity and rupture models.

Characterization of the Structural Typologies of Buildings in the Lima Metropolitan Area

The Lima metropolitan area is in a prone earthquake zone, which is exposed to a seismic gap; this can result in Mw 8.9 megathrust earthquake in the central Peru. After the Pisco earthquake in 2007, risk management policies changed in Peru and are improving annually. Thus, more resources are destinated to assessing earthquake hazard, vulnerability, and risk in districts of the Lima metropolitan area mainly; nevertheless, they are limited to cover in detailed the whole extension of probable affected area after this potential megathrust earthquake. Data of buildings in the Lima metropolitan area were analyzed in this paper, to provide useful information in the development of rapid methodologies of identification of buildings. The Japan Peru Center for Earthquake Engineering and Disaster Mitigation (CISMID) gathered these data from 2010 to 2021 in field surveys to conduct vulnerability and risk studies; the survey of building characteristics consisted of obtain mainly the number of stories, predominant material, structural systems, type of occupancy, and state of conservation. Vulnerability and risk studies for districts of the Lima metropolitan area were conducted by considering one representative building in one block. Results showed that the predominant material in the Lima metropolitan area is masonry, used in different structural systems, such as confined masonry and other which are nonengineered structures. Also, two-story buildings are predominant in the target area, followed by one and three-stories buildings. Risk assessment for the Lima metropolitan area and the study area were conducted using the data from the characterization of structural typologies obtained in this study. Approximately, 47.72% and 58.67% of buildings presented a very high-risk level in the Lima metropolitan area and the study area, respectively, under the expected earthquake scenario due to the seismic gap in the central Peru.

Numerical modelling of the 1970 intraslab Peru earthquake and tsunami (Mw 7.9)

Numerical modelling of the 1970 intraslab Peru earthquake and tsunami (Mw 7.9)

Factors Associated with Knowledge of Evacuation Routes and Having an Emergency Backpack in Individuals Affected by a Major Earthquake in Piura, Peru.

Information on the prevention of earthquakes in Peru, a high-risk country, is still emerging. We determined the frequency and factors associated with knowledge of evacuation routes and the use of emergency backpacks in people affected by a major earthquake. A cross-sectional study using secondary data was conducted from August-December 2021 on people that experienced the 6.1 magnitude earthquake that occurred in Piura, Peru on 30 July 2021. The outcome was self-reported knowledge of evacuation routes and the use of emergency backpacks. The association with self-reported earthquake preparation training, use of sources of information on earthquakes, and sociodemographic variables was investigated. A total of 69.5% of participants knew evacuation routes, and 46.3% had an emergency backpack. A higher frequency of knowledge of evacuation routes was associated with previous training (PR: 1.47; 95% CI: 1.15-1.87), use of the media (PR: 1.35; 95% CI: 1.06-1.72), having received information from the COEN (PR: 1.19; 95% CI: 1.02-1.40), and with a greater number of household members (PR: 1.03; 95% CI: 1.01-1.06). There is a high frequency of knowledge of evacuation routes among participants. However, basic notions of prevention culture are still needed. This research contributes to policy development on earthquake preparation at the community level.

Self-reactivated rupture during the 2019 Mw = 8 northern Peru intraslab earthquake

The 2019/05/26 Northern Peru earthquake (Mw=8) is a major intermediate-depth earthquake that occurred close to the eastern edge of the Nazca slab flat area. We analyze its rupture process using high-frequency back-projection and seismo-geodetic broadband inversion. The latter approach shows that the earthquake propagated with almost purely normal faulting along the 60° eastward dipping plane. Both imaging techniques provide a very consistent image of the peculiar space-time rupture process of this earthquake: its 60-second long rupture is characterized both by a main northward propagation (resulting in a rupture extent of almost 200 km in this direction) and by a reactivation phase of the hypocentral area, particularly active 35 s to 50 s after origin time. Given the depth of this earthquake (125-140 km), the reactivation time window coincides with the arrival time of the surface-reflected elastic wavefield. Computed values of the dynamic Coulomb stresses associated with this wavefield are of the order of ten to several tens of kPa, in a range of values where dynamic triggering has already been observed. The reactivation phase of the Peru earthquake may thus originate from fault areas that were brought close to rupture by the initial rupture front before being triggered by stress increments provided by the reflected wavefield. Source time function complexity observed for other large intermediate-depth earthquakes further suggests that such a mechanism is not an isolated case.

Estimation of the finite fault source model for the 2018 Mw7.1 Acari, Peru earthquake using a hybrid simulation prediction approach

The near-field motion of large earthquakes is generally simulated using finite fault source models (FFSMs). Most of these models use post-earthquake observation data as the constraints for the inversion model, and therefore, it is difficult to generate FFSMs until after the earthquake has occurred. We use parameters from previous earthquakes to generate FFSMs in a hybrid simulation prediction approach that combines the asperity model and the k−2 model. New scaling laws for global and local parameters are used to estimate the asperity model parameters and the coordinates of the fracture initiation point. Using the k−2 model, 30 sets of FFSMs are established using truncated normal distributions and several regional geological structural parameters. After applying the residual evaluation criteria to the various response spectra, we select the average source model. We then apply our methodology to the 2018 Acari earthquake in Peru. Both our average model and the USGS inversion model have two asperities, but their positions are different. The response spectra of the four representative points of our model are similar to those of the USGS model, and the peak difference is between −13.4% and 18.4%. The USGS model is a post-earthquake model, which requires many parameters and post-earthquake observation data. Our FFSM requires few parameters and represents the most representative source model for future earthquakes in this area with similar magnitudes, and it is intended to be supplementary to the inversion model. Therefore, our hybrid approach may be used for the early prediction or rapid estimation of the resulting ground motions.

Seismic Source of 1966 Huacho Peru Earthquake (Mw 8.1) from Tsunami Waveform Inversion

Seismic Source of 1966 Huacho Peru Earthquake (Mw 8.1) from Tsunami Waveform Inversion

Could thermal pressurization have induced the frequency-dependent rupture during the 2019 Mw8.0 Peru intermediate-depth earthquake?

SUMMARY The rupture process of earthquakes at intermediate-depth (∼70–300 km) have rarely been illuminated by a joint analysis of geodetic and seismic observations, hindering our understanding of their dynamic rupture mechanisms. Here we present detailed rupture process of the 2019 Mw8.0 Peru earthquake at the depth of 122 km depth, derived with a holistic approach reconciling InSAR and broad-band seismic waveform data. The joint inversion of InSAR observations and teleseismic body waves results in a finite rupture model that extends ∼200 km along strike, with unilateral rupture towards north that lasted for ∼60 s. There are four major slip patches in the finite fault model which are well corresponding to the position and timing of the sources in back-projection and multiple points source results. The largest slip patch, which occurred ∼40 s after the rupture initiation, had a longer and smoother rise time, and radiated much weaker high-frequency seismic waves compared to other smaller slip patches. This distinct frequency-dependent rupture could be explained by a strong dynamic weakening mechanism. We question whether thermal pressurization of pore free water rather than thermal run away could be such a mechanism. Our frequency content analysis could be generalized to study other earthquakes including those deeper than 300 km.

Mental Health Disturbance after a Major Earthquake in Northern Peru: A Preliminary, Cross-Sectional Study

Little has been studied in Peru on the mental health repercussions after a major earthquake. We aimed to explore the factors associated with depressive and anxiety symptoms in people who experienced a 6.1 magnitude earthquake in Piura, Peru, on 30 July 2021. A preliminary cross-sectional study was conducted in the general population between August–September 2021. An online questionnaire was provided using PHQ-9, GAD-7, and other relevant measures. Generalized linear models were applied. Of the 177 participants, the median age was 22 years, the majority were female (56%), and many experienced depressive (52%) or anxiety symptoms (52%). Presence of depressive symptoms was associated with a personal history of mental disorder, moderate housing damage, social/material support from politicians, moderate food insecurity, and insomnia. Presence of anxiety symptoms was associated with physical injury caused by the earthquake, mild food insecurity, and insomnia. The development of depressive and anxiety symptoms following the 2021 earthquake experienced in Piura depended on multiple individual and socioeconomic factors. Additional studies should reinforce the factors identified here given the methodological limitations, such as the study design, sampling method, and sample size. This would lead to effective intervention measures to mitigate the impact of earthquakes on mental health.

Slab metamorphism and interface earthquakes in Peru: Implications from three-dimensional hydrothermal variation in the subducted Nazca plate

Convergent plate dehydration is of significance in determining the coupling strength and seismicity activity at variable subduction contacts. Characterized by decadal M > 7.5 devastating earthquakes offshore and a lack of a magmatic arc in north-central Peru, the Peruvian megathrust remains enigmatic in terms of the along-strike heterogeneity of the thermal regime, slab dehydration, and seismotectonics. Hydrothermally controlled petrological metamorphism of multiple facies within the subducted oceanic lithosphere and subsequent fluid channeling and migration lead to fault instability and seismic and aseismic slips on the megathrusts. Based on 3D thermal modeling, we estimate the features of the Peruvian subduction hydrothermal regime. Our results show that (1) the shallow seismogenic zone (M > 7.5 earthquakes) along coastal Peru exhibits high slab dehydration rates and gradients and is associated with fault segmentation and the updip migration of fluids controlling the occurrence of great megathrust earthquakes; (2) the low slab dehydration rate (<0.01 wt%/km) in north Peru contributes to the absent volcanism in north Peru, while the high slab dehydration rate (>0.02 wt%/km) beneath south Peru facilitate the recurrence of magmatic volcanism; (3) the subduction-related slip behaviors at a certain depth resulting from heterogeneous variations in the coupled plate interface are determined by slab dehydration and petrological metamorphism in the subducted Nazca plate. The variation in slab dehydration contributes to the seismotectonic segmentation and slip variation associated with changes in the pore fluid pressure on the subducted megathrust.

Efficacy and Usefulness of an Independent Public Earthquake Early Warning System: A Case Study—The Earthquake Network Initiative in Peru

Abstract Public earthquake early warning (PEEW) systems are intended to reduce individual risk by warning people ahead of shaking and allowing them to take protective action. Yet very few studies have assessed their actual efficacy from a risk-reduction perspective. Moreover, according to these studies, a majority of people do not undertake safety actions when receiving the warning. The spectrum of PEEW systems has expanded, with a greater diversity of actors (from citizens to private companies), increased independence from national authorities, and greater internationality. Beyond differences in warning and messaging strategies, systems’ characteristics may impact the way the public perceive, trust, understand, and respond to these warnings, which in turn will influence PEEW systems’ efficacy and perceived usefulness, enhancing the need for additional research. We take the example of earthquake network, an independent, voluntary, community-based and free system that offers a PEEW service. Through a quantitative survey (n = 2625), we studied users’ perception and reaction to a warning sent related to an M 8.0 earthquake in Peru (where no national system existed). We observed that even though only a minority of users actually took protective action, the system was appreciated and perceived as useful by the majority because it enabled mental preparation before the shaking. We found evidence for a tolerance for perceived late, missed, and false alerts. However, because it is a voluntary and independent system, the social dimension of the warning was incomplete because only a fringe of the population benefited from the warning. Therefore, many users’ first reaction was to warn their relatives. We discuss the need for partnerships between PEEW operators and national authorities to guarantee universal access to the service and maximize PEEW system efficacy.

Evaluation of GRACE/GRACE Follow-On Time-Variable Gravity Field Models for Earthquake Detection above Mw8.0s in Spectral Domain

This study compares the Gravity Recovery And Climate Experiment (GRACE)/GRACE Follow-On (GFO) errors with the coseismic gravity variations generated by earthquakes above Mw8.0s that occurred during April 2002~June 2017 and evaluates the influence of monthly model errors on the coseismic signal detection. The results show that the precision of GFO monthly models is approximately 38% higher than that of the GRACE monthly model and all the detected earthquakes have signal-to-noise ratio (SNR) larger than 1.8. The study concludes that the precision of the time-variable gravity fields should be improved by at least one order in order to detect all the coseismic gravity signals of earthquakes with M ≥ 8.0. By comparing the spectral intensity distribution of the GFO stack errors and the 2019 Mw8.0 Peru earthquake, it is found that the precision of the current GFO monthly model meets the requirement to detect the coseismic signal of the earthquake. However, due to the limited time length of the observations and the interference of the hydrological signal, the coseismic signals are, in practice, difficult to extract currently.

Back-propagating rupture evolution within a curved slab during the 2019 Mw 8.0 Peru intraslab earthquake

SUMMARY The 26 May 2019 MW 8.0 Peru intraslab earthquake ruptured the subducting Nazca Plate where the dip angle of the slab increases sharply and the strike angle rotates clockwise from the epicentre to north. To obtain a detailed seismic source model of the 2019 Peru earthquake, including not only the rupture evolution but also the spatiotemporal distribution of focal mechanisms, we performed comprehensive seismic waveform analyses using both a newly developed flexible finite-fault teleseismic waveform inversion method and a back-projection method. The source model revealed a complex rupture process involving a back-propagating rupture. The initial rupture propagated downdip from the hypocentre, then unilaterally northward along the strike of the slab. Following a large slip occurring ∼50–100 km north of the hypocentre, the rupture propagated bilaterally both further northward and back southward. The spatial distribution of focal mechanisms shows that the direction of T-axis azimuth gradually rotated clockwise from the epicentre northward, corresponding to the clockwise rotation of the strike of the subducting Nazca Plate, and the large-slip area corresponds to the high-curvature area of the slab iso-depth lines. Our results show that the complex rupture process, including the focal-mechanism transition, of the Peru earthquake was related to the slab geometry of the subducting Nazca Plate.

Seismic source characteristics of the intermediate-depth and intraslab 2019 northern Peru earthquake (Mw 8.0)

On May 26, 2019, an unusual depth-intermediate focus earthquake, in the interior of the Nazca plate, shook the northern Peruvian jungle and caused the death of two victims. This earthquake was felt in almost all of Peru as well as Brazil, Ecuador and Colombia. The focal mechanism calculated is of the normal fault type (strike = 353∘, dip = 57∘, rake = − 99∘) for a focal depth of 114 km. The slip distribution was obtained through an inversion process of teleseismic waveforms. The maximum slip was 6.3 m, located around the central side of the fault plane. The moment magnitude calculated was Mw 8.0; the spectral analysis indicated a similar magnitude of Mw 8.0. The source time function indicates a multiple rupture earthquake, with the presence of several pulses of seismic energy release, with a total duration around 80 s. The rupture directivity was from the south to the north; we have assumed a propagation rupture velocity of 2.8 km/s. The modeled fault plane geometry has dimensions of 208×105 km2. The predicted vertical coseismic deformation field shows a pattern of mostly subsidence.

Anomalously low aftershock productivity of the 2019 MW 8.0 energetic intermediate-depth faulting beneath Peru

The 26 May 2019 Peru (MW 8.0) earthquake struck within the nearly-horizontal underthrust Nazca plate at depths from ∼110 to 150 km below the upper Amazon, near a steep bend in the plate where it plunges down to a deep earthquake zone. Little prior seismicity occurred in this region, but large intraslab events with similar normal-faulting mechanisms have occurred to the west. The event is situated in a similar slab position to the 2017 Puebla-Morelos, Mexico earthquake, but the remote location resulted in limited loss of life and damage. Back-projection imaging and finite-fault inversion based on teleseismic data suggest a brittle and energetic rupture process with unilateral expansion northward over a 170-km-long zone at a rupture speed, Vr ∼3 km/s, with three normal-faulting patches of up to ∼4.5 m slip. Despite the mainshock size, it produced only three M4.0+ aftershocks within 300 km (one nearby); the aftershock productivity of the 2019 Peru earthquake is very low even among all large intermediate-depth earthquakes, but similar to that for other large Peruvian intraslab events. Comparison of aftershock productivity of the Peru event with that of global large earthquakes in various tectonic settings suggests that the low aftershock productivity can largely be attributed to regionally homogeneous faulting systems and relatively uniform stress state in the flat Peru slab.

An interdisciplinary approach to identify zones vulnerable to earthquakes

Earthquakes in Peru are responsible for enormous material and human losses. One of the reasons for the latter is that risk and disaster management policies do not consider individuals as a significant factor for planning post-disaster activities. An understanding of all-important aspects that influence post-disaster efforts would reduce the number of dead, injured and affected people as well as the required money and time to invest. This research develops an interdisciplinary approach, based on seismic vulnerability, to identify those zones that need immediate attention after an earthquake. We consider vulnerability to be a result of two dimensions: social and physical. The first describes society by its anthropogenic characteristics through social indicators (age, daily income, education, etc.). The second describes the built environment and the main features of infrastructure. The results show that the physical and social dimensions intersect and interact with fairly consistent regularity. Thus, we are then able to more accurately identify the areas that require higher prioritization in an emergency scenario. Having this data available for regions predisposed to earthquakes will allow for substantial improvements to current risk mitigation action plans as well as the promotion of a more comprehensive prevention effort.

Using knowledge management to improve inter-institutional collaboration in crisis events

The aim of the study is to propose policy guidelines that can help to improve the likelihood of success in crisis events, highlighting the need of better knowledge management to improve crisis management. After a brief analysis of three crisis events occurred in the USA, Chile and Peru, the study deepens in the situation that was lived in the Peru's earthquake. Furthermore, an innovative model of inter-institutional collaboration based on the concept of open data as a tool for knowledge management is proposed, obtaining information from the problems encountered in situations of crisis that occurred previously. Three groups of stakeholders (academics, public servants and citizens) validated the proposed policy guidelines and the open data model. Finally, this study can serve as a starting point for the development of an open data platform that helps society to face crisis events through knowledge management, promoting transparency, participation and collaboration among stakeholders.

Using knowledge management to improve inter-institutional collaboration in crisis events

The aim of the study is to propose policy guidelines that can help to improve the likelihood of success in crisis events, highlighting the need of better knowledge management to improve crisis management. After a brief analysis of three crisis events occurred in the USA, Chile and Peru, the study deepens in the situation that was lived in the Peru's earthquake. Furthermore, an innovative model of inter-institutional collaboration based on the concept of open data as a tool for knowledge management is proposed, obtaining information from the problems encountered in situations of crisis that occurred previously. Three groups of stakeholders (academics, public servants and citizens) validated the proposed policy guidelines and the open data model. Finally, this study can serve as a starting point for the development of an open data platform that helps society to face crisis events through knowledge management, promoting transparency, participation and collaboration among stakeholders.

Precursor Variability of Lineament Systems Detected Using Satellite Images during Strong Earthquakes

The possibility of using the dynamics of lineament systems as precursors of seismic events has been studied based on the example of strong earthquakes (M ≥ 5) in California (United States), Peru, Iran, Turkey, Transbaikalia, and Kamchatka, as well as in other regions. The pattern and time intervals of changes in lineament systems during earthquake preparation and occurrence are analyzed. It is shown that the features of changes in rose diagrams, ratios of total lengths of local lineaments (strokes) of different directions, orientation of elongation lines of rose diagram of strokes, and other characteristics that were revealed using satellite images can be used as mid- and short-term precursors of seismic events. A methodology for the automated lineament analysis of satellite images is suggested and prospects of its development for monitoring seismically dangerous areas are determined.