Mexico Earthquake Research Articles

Damage assessment and seismic behavior of steel buildings during the Mexico earthquake of 19 September 2017

During the 19 September 2017 earthquake, steel buildings in the States of Morelos, Puebla, Mexico, and Mexico City were subjected to severe ground shaking. Despite in some cases, moderate damages in non-structural elements were developed; generally, null or minor structural damage was reported. The notable exceptions are (1) a three-stories building located at the southern area of Mexico City and (2) some schools near to the epicentral region in the State of Morelos. The behavior of these buildings is analyzed in detail. Conclusions are drawn on the demands imposed on steel structures considering the actual demands in order to underline the relevance of the normative design procedures.

Seismic risk of sliding ground-mounted rigid equipment

This study discusses a general formulation for risk assessment of ground-mounted rigid sliding equipment and contents during earthquakes. The displacement and acceleration response of blocks during earthquakes and risk were examined for four types of support conditions: (1) equipment simply supported on a foundation; (2) equipment restrained to a fixed base; (3) equipment supported on a linear viscoelastic isolation system; and (4) equipment supported on a single concave spherical sliding (SCSS) isolation system. Because empirical fragility functions for sliding-dominated equipment remain insufficient, the present study relies on numerical analysis and a solid physical background to compute risk. These results should aid designers in the selection of appropriate support conditions or mitigation measures for rigid equipment and contents in seismic-prone regions.As an example, the seismic response of rigid equipment is illustrated using ground motions from the recent (2017) Mexico earthquakes, which damaged several pieces of equipment in the largest oil refinery in Mexico. Furthermore, the effects of site-to-source distance for sites located on firm soil are studied in detail, as the frequency content of these ground motions differ significantly and play a key role in the reliability of sliding blocks. The results of the seismic risk assessment show that low-frequency ground motions (i.e., far-field site) generally yield lower maximum and residual equipment displacements compared to those from high-frequency ground motions (i.e., near-source site). This investigation also concludes that the reliability of freestanding and base-isolated equipment in terms of maximum absolute block accelerations is higher than that of anchored equipment.

COMUNICACIÓN GUBERNAMENTAL RESPONSABLE EN SITUACIONES DE CRISIS: EL CASO DE FRIDA SOFÍA

Within the framework of expectations that the 21st century’s society demands, the economic, political and environmental crises that various countries face have forced corporations and public institutions to re-evaluate the fragility that the environment represents for their activities. In this way, the role played by communication as a strategic element to preserve corporate image and reputation becomes essential. The present research aims to analyze the institutional discourse of public spokesmen before a national crisis situation, and thus, contribute to the axis of responsible communication of organizations. In view of the foregoing, we analyzed the case of crisis known as Frida Sofia”, which derived from the earthquake in Mexico on September 19, 2014. Based on the methodology proposed by Grice, an analysis of the oral and written discourse of the main spokespersons of the governmental institution Secretaria de Marina (SEMAR) was carried out, with the purpose of establishing their discursive responsibility within the context of crisis. The research responds to a documentary-interpretative nature, which is based on pragmatics; a field of study which analyzes the way in which the context influences the interpretation and meaning of a certain event. The axis of responsible communication refers to a committed act of the organizations, whose main characteristic is the constant and honest dialogue between the entity and its spokespersons; elements that, in different contexts and situations, allows for a more sensitive crisis management and less affection for the institution at stake.

The September 19, 2017 Mw 7.1 Puebla-Mexico City earthquake: Observed rockfall and landslide activity

This note documents key observations of slope instability and rockfall activity made by the UNAM-GEER reconnaissance team after the Mw 7.1 Puebla-Mexico City earthquake of September 19, 2017. The investigated sites were located in Mexico City and the states of Morelos, Puebla and Mexico. Sites were studied using a combination of ground surveys, UAV imagery, and terrestrial LiDAR imaging. The field reconnaissance efforts were supplemented by analysis of pre- and post-event satellite images to define the boundary of the region affected by earthquake-induced landslides. Most slope failures occurred in remote areas or areas that had a prior history of instability. Overall, the consequences of slope instabilities caused by the 2017 Puebla-Mexico City earthquake were relatively minor compared with the reported structural damage. More than 360 deaths were attributed to this earthquake of which one death was attributed to landslide activities. The size of the area affected by landslides and the intensity of shaking in these areas was consistent with relationships developed in previous studies. The lack of major effects from earthquake-induced landslides is consistent with previous earthquakes in central and southern Mexico and stands in sharp contrast to many parts of Central America where earthquake-induced landslides pose a significant hazard.

Delayed and Sustained Remote Triggering of Small Earthquakes in the San Jacinto Fault Region by the 2014 Mw 7.2 Papanoa, Mexico Earthquake

AbstractWe apply a move max matched‐filter method to detect heightened seismicity triggered in the San Jacinto fault (SJF) zone, by the 2014 Mw 7.2 Papanoa, Mexico earthquake. The move max matched filter detects 5.4 and 1.7 times the number of earthquakes in the Southern California Seismic Network catalog and those detected by the matched‐filter method, respectively. The seismicity rate increases significantly ~3.5 hr after the passage of the teleseismic waves and persists above the background level for about 1 week. This observation of delayed triggering may imply that dynamic stresses had initiated a time‐dependent advance to failure or a secondary process. A highly active triggered patch is located ~10 km west of the SJF near Anza, on a previously unmapped fault. Focal mechanisms and a best fit plane suggest a normal fault perpendicular to the SJF. The unmapped fault may indicate higher seismic hazard in the surrounding areas if a large earthquake nucleated around the Anza seismic gap.

Spatial Distribution of Radiated Seismic Energy of Three Aftershocks Sequences at Guerrero, Mexico, Subduction Zone

AbstractGeneral characteristics of seismic energy release of thrust earthquakes in Mexico have been reviewed in the past; however, a detailed analysis can contribute to a better understanding of the mechanisms that control its distribution along the Guerrero, Mexico, subduction zone. To address it, we obtain the source spectra of the 2012 Mw 7.5 Ometepec‐Pinotepa Nacional, the 2014 Mw 7.2 Papanoa, and the 2018 Mw 7.2 Pinotepa Nacional earthquakes, as well as of their M≥4.0 aftershocks to estimate their seismic moment M0 and radiated seismic energy ES. The first and the last sequences occurred at the southern border of the Guerrero seismic gap, a region where no significant earthquake (M>7.0) has occurred at least in the last century; whereas the second sequence was located at the northern edge of the same seismic gap. The mean value of the log of radiated seismic energy scaled with the seismic moment, log(e˜)=log(ES/M0), for this set of earthquakes is −5.05±0.25. We classify the analyzed events into four regions, two in the southern edge of the gap and two in the northern one. At both ends, there is one region that shows regular values of log(e˜) (−4.64±0.25 and −4.62±0.25), whereas the other one shows low values of log(e˜) (−5.40±0.25 and −5.55±0.25) that could be related to a possible slow‐rupture behavior. These last regions are identified near the trench at southern Guerrero coast and immediately outside the northern end of the seismic gap. The distribution of log(e˜) is spatially heterogeneous along the trench, suggesting variations on the shear strength and coupling at the interface.

Prevalence of Post-traumatic Stress Disorder and Depression After the September 19th, 2017 Earthquake in Mexico

Natural disasters cause mental disorders, the most frequent are Post-traumatic stress disorder (PTSD) and depression, which should be quickly identified for immediate psychological care. The aim of this study was to estimate the frequency of these disturbances in a population with social security, located in the states hit by the earthquake that took place on September 19th, 2017 in Mexico. To identify persons with PTSD and depression, a random sample of the population was screened (1-2months' post-earthquake) in primary health care clinics at the Mexican Institute of Social Security (IMSS). A questionnaire for the detection of mental conditions (The Screening Questionnaire for Disaster Mental Health, SQD) was used to select people for group therapy and/or psychotherapeutic support, when identified with severe PTSD and high risk of depression. Over 44,855 persons (67.9% females, 32.1% males), residents of Mexico City, the State of Mexico, Puebla, Morelos were surveyed. The prevalence of severe PTSD was 11.9% and depression 9.2%. The highest prevalence of PTSD was observed in Mexico City (12.8%) the state with more material damage. Women were at higher risk for PTSD (OR, 2.08; 95% CI 1.97-2.19, p=0.000) and depression (OR, 1.86; 95% CI 1.72-2.01, p=0.000). The prevalence of PTSD and depression was higher in those states with severe damage caused by the earthquake; women were more susceptible to mental disorders.

InSAR full-resolution analysis of the 2017–2018 M>6 earthquakes in Mexico

The present study analyzes the sequence of 4 important earthquakes occurred in Mexico from September 2017 to February 2018, exploiting the large availability of InSAR data and analytical models, with a twofold goal: to privede new solutions for seismogenic sources, completely independent from seismological data, and to discuss methodological aspects related to the non-linear and linear inverse problem. We review and update an earlier study, focused on the concept of resolution, showing the level of detail achievable in the investigation of the slip distribution based on geodetic observations, according to data availability, fault locations and event magnitudes. We further give new insights into the relationship between fault resolution and parameter uncertainty, demonstrating that a realistic assessment is strictly related to a proper fault subdivision. We eventually discourage the use of qualitative approaches, such as the checkerboard test, to evaluate the data resolving power and suggest the adoption of quantitative indicators, like the Dirichlet Spread Function, normalized, easy to calculate and mathematically robust.

SEISMO-MAGNETIC FIELD ANOMALIES DETECTION USING SWARM SATELLITES (ALPHA, BRAVO AND CHARLIE)

Abstract. Among the lithospheric, atmospheric and ionospheric earthquake precursors, it seems that the ionospheric anomalies showing a meaningful association with seismic activities during absence of solar and geomagnetic activities. Unfortunately there are a limited number of satellite sensors to survey the ionosphere and study on seismo-ionospheric anomalies. This paper represents the data analysis results of Swarm satellites including Alpha, Bravo and Charlie data around the Mexico (September 8, 2017) earthquake. The orbital analysis and time series of magnetic field parameters (magnetic scalar and vectors (X, Y, Z) components) inside the Dobrovolsky’s area show anomalous variations close to the time and locations of the Mexico earthquake. There is a concavity or convexity variations in the some of the time-series to the centre of the earthquake day. In other words, from about 90 days before the event a decreasing or increasing trend in variations of parameters is observed and exactly after the earthquake day its trend changes. It should be noted that the variations of the solar and geomagnetic indices must indicate a normal behaviour during the observed seismo-ionospheric anomalies. Therefore this study indicates that the Swarm satellites measurements play an undeniable role in progress the studies of the ionospheric precursors.

Afrontamiento y síntomas de estrés postraumático en niños mexicanos después del sismo de 2017

Se analiza la relación entre el afrontamiento frente a riesgos extremos y los síntomas de estrés postraumático en niños que experimentaron el terremoto de México del 2017. Al mes del evento fueron evaluados 178 niños/as entre 11 y 15 años de edad (Media = 12.90, DE= 1.05) del municipio de Malinalco al sur del Estado de México, con las Escalas de Afrontamiento frente a Riesgos Extremos y la Escala Infantil de Síntomas del Trastorno de Estrés Postraumático (TEPT). Lo resultados mostraron puntajes altos en TEPT especialmente en las niñas. Se confirma la hipótesis de relación entre ambas variables. Se sugiere analizar la capacidad resiliente ante la exposición de este tipo de desastres naturales, y dar un seguimiento a los mismos.

Seismicity Monitoring in North-Central New Mexico by the Los Alamos Seismic Network

AbstractThe first seismic stations of the Los Alamos Seismic Network (LASN) were installed in 1973, as a part of research on monitoring of nuclear testing. The extent of the network rapidly expanded by the late 1970s. By the middle 1980s, spatial coverage of the network was drastically reduced, due to a loss of funding. Since then, however, it has been possible to expand the coverage of the network with additional stations and to slowly upgrade network equipment to match contemporary instrument standards. These improvements will make it possible to keep recording the network’s data and to initiate real-time exchange of data with other institutions to improve earthquake monitoring throughout New Mexico and neighboring states. During more than 40 yr of operation, the network has provided a slow but steady increase in the volume of earthquake seismograms available to study seismicity and tectonics in north-central New Mexico. The current network covers an area from the Valles Caldera on the west, to within the Rio Grande rift on the east. LASN has yielded locations for about 900 earthquakes in north-central New Mexico between 1973 and 2013 (the most recent locations available). Epicenters of these have a complex pattern, with some that can be attributed to the deformation of the rift, though most are spread in areas west of the rift. A lack of seismicity in and near the Valles Caldera reinforces an earlier observation, based on far fewer earthquakes, which first called attention to this paucity of seismicity and attributed it to ductile deformation resulting from elevated crustal temperatures.

The Tesistan, Mexico earthquake (Mw 4.9) of 11 May 2016: seismic-tectonic environment and resonance vulnerability on buildings

To highlight the importance of small earthquakes in seismic hazard, a study of the 11 May 2016, Mw 4.9, Tesistan, Mexico earthquake is presented. Due to the close proximity of the event to the city, accelerations were considerably higher than those caused by historical severe earthquakes (6.0 < Mw < 8.2). This paper addresses two objectives related to the Tesistan event: the first is to estimate the focal mechanism solution in order to place the event in the context of the tectonic environment of this area. The second is focused on a vulnerability evaluation of buildings that suffered resonance. Several building’s typologies with variations in construction system and height are assessed in terms of resonance with the structural and soil periods. The results show that around the Zapopan station, strong damage is expected in intermediate to high-rise buildings (12–30 m) with moment resistant frame systems and in reinforced concrete shear walls. Masonry structures around this station may not present resonance. In contrast, in the surroundings of the Guadalajara station, all intermediate height buildings from 9 to 21 m may present resonance.

The Tesistan, Mexico Earthquake (Mw 4.9) of 11 May 2016: Tectonic, Seismic Environment and Ground Motion Analysis

To highlight the importance of small earthquakes in seismic hazard, we present a study of the 11 May 2016, Mw 4.9, Tesistan earthquake. According to historical data from instrumental seismicity, this earthquake represents the largest event recorded near Guadalajara. Due to the close proximity of the event to the city, accelerations were considerable higher than those caused by historical severe earthquakes. From the analysis of regional seismicity, its occurrence: (i) shows a clear correlation with seismicity in the subduction zone and (ii) appears to be related to tectonic activity along a previously unmapped SE extension of the faults which form the northern wall of the Plan de Barrancas/Santa Rosa Graben, located to the northwest within the more regional Tepic-Zacoalco Rift. The analysis of the two strong ground motions recorded within the city reveals considerable site effects.

Rapid determination of source parameters for the 2017 Mw 8.2 Mexico earthquake based on high-rate GPS data

Aiming to rapidly determine source parameters (i.e., static offset, seismic wave arrival, moment magnitude, and hypocentral location) for the Mexico 8.2 earthquake, the records of 7 high-rate GPS stations are utilized. Smoothness Priors Method (SPM) is introduced to rapidly extract the static offset from GPS displacement waveforms, and the result suggests this approach is feasible. The seismic wave arrival detection is carried out with the aid of S-transform, and the propagation velocity of seismic wave detected by most GPS stations are within 4–5 km/s, implying the seismic wave captured by GPS station may be S wave or surface wave. After that, an empirical regression model is adopted to characterize the moment magnitude for this earthquake, and this empirical formula can obtain reliable magnitude in comparison with the reference magnitude. The convergence time of average moment magnitude is 298 s, suggesting that a reliable and robust magnitude (Mw 8.37) can be estimated by the 7 GPS stations with about 298 s after earthquake occurrence. Considering the influence of the spatial distribution of GPS stations, 4 nearest GPS stations evenly distributed on both sides of the fault are selected to determine the warning-magnitude for the Earthquake Early Warning (EEW). A reliable and robust moment magnitude (Mw 8.2) can be estimated by the 4 stations with about 251 s, which is 57 s ahead of 7 stations. Finally, the coordinates of 6 GPS stations and corresponding seismic wave arrival time are utilized to determine the hypocentral location, and the latitude and longitude of estimated location is 14.925°N and 93.765°W, which is 17.9 km from the reference location. The results indicate that the source parameters required for EEW can be rapidly determined based on high-rate GPS displacement waveforms, and integrating real-time GPS into a joint EEW system will be crucial going forward.

Recycled Rubber Fiber Reinforced Bearings (RR-FRBs) as base isolators for residential buildings in developing countries: The demonstration building of Pasir Badak, Indonesia

The aftermath of the Mw 7.1 Central Mexico earthquake struck at 13:14 CDT on 19 September 2017 confirmed, once again, the need of introducing seismic mitigation technologies that can effectively be implemented on a wide scale to reduce the seismic risk in developing regions of the world. With this in mind, the aim of this paper is the validation of Recycled Rubber-Fiber Reinforced Bearings (RR-FRBs) as base isolation devices for low-cost houses in developing counties.Results of Response History Analyses (RHAs) of a RR-FRBs base isolated residential building are discussed in this work, together with the design, Finite Element Analyses (FEAs), manufacturing and testing of full-scale prototype bearings for the building under investigation. In addition, the seismic performance of the RR-FRBs base isolated structure is compared to the response of the same building when isolated at the base with conventional devices, namely Laminated Rubber Bearings (LRBs) and Friction Pendulum Systems (FPSs).Results of this work underline the high potential of these low-cost bearings as base isolation devices for residential buildings, confirming the possibility of achieving a significant improvement of the seismic performance of ordinary structures by using the low-cost and easy to manufacture RR-FRBs.

Posttraumatic stress symptoms in people exposed to the 2017 earthquakes in Mexico

This is the first study to produce a reliable valid measure of the symptoms of Posttraumatic Stress Disorders (PTSD) in Mexico, which has a high incidence of disasters, and has not had a measurement of PTSD frequency in the population. The objective was to analyze the prevalence of PTSD symptoms in persons who experienced the 2017 earthquakes in Mexico. A probabilistic sample of 1539 participants from Mexico City, the State of Mexico, Chiapas, Puebla, Morelos and Oaxaca during November and December of 2017 was screened using the Davidson Trauma Scale (DTS) for symptoms of post-traumatic stress. The prevalence of PTSD symptoms was 34.6%, with greater effects on the inhabitants of Oaxaca, Morelos and Puebla, women, indigenous people and people who experienced damage to their homes (p = 0.001). The DTS had a moderate negative correlation with the RS-14 and a Cronbach's alpha coefficient of 0.957. The confirmatory factor analysis generated four factors that explain 50% of the variance, compatible with a Dysphoria model. We can conclude that one in three people exposed to earthquakes had symptoms of post-traumatic stress.

Nonlinear optimal control for reducing vibrations in civil structures using smart devices

The frequently excessive vibrations presented in civil structures during seismic events or service conditions may result in users\' discomfort, or worst, in structures failure, producing economic and even human casualties. This work contributes in proposing the synthesis of a nonlinear optimal control strategy for semiactive structural control, with the main characteristic that the synthesis considers both the structure model and the semiactive actuator nonlinear dynamics, which produces a nonlinear system that requires a nonlinear controller design. The aim is to reduce the unwanted vibrations in the response of civil structures, by means of intelligent fluid semiactive actuator such as the Magnetorheological Damper (MRD), which is a device with a low level of power consumption. The civil structures for which the proposed control methodology can be applied are those admitting a state-dependent coefficient factorized representation model, such as buildings, bridges, among others. A scaled model of a three storey building is analyzed as a case study, whose dynamical response involves displacement, velocity and acceleration of each one of the storeys, subjected to the North-South component of the September 19th., 2017, Puebla-Morelos (7.1M), Mexico earthquake. The investigation rests on comparing the structural response over time for two different conditions: with no control device installed and with one MRD installed between the first floor and the ground, where a nonlinear optimal signal for the MRD input voltage is determined. Simulation results are presented to show the effectiveness of the proposed controller for reducing the building\'s dynamical response.

Evidence for Rupture Through a Double Benioff Zone During the 2017 Mw 8.2 Chiapas, Mexico Earthquake

AbstractWe combine multi‐array relative back‐projection of high‐frequency P waves and finite‐fault modeling of low‐frequency P waves from the 8 September 2017 Mw 8.2 Chiapas, Mexico earthquake to image unilateral rupture on a southeast‐northwest striking subvertical fault plane over depths of 10–70 km. Improved multi‐array relative back‐projection estimates of rupture speed and fault geometry provide key refinements to the slip model from finite‐fault modeling. Compilation of prior seismicity and aftershocks reveals the earthquake initiated in the lower plane of a double Benioff zone (DBZ) and ruptured with large slip across the entire DBZ. The previously aseismic interior does not appear to be due to lack of stress as both planes show downdip extension stresses. Instead, tomographic imaging of DBZs find high Poisson's ratio with fast velocities in the DBZ interior, so we propose that highly hydrated harzburgite generates velocity‐strengthening behavior that inhibits earthquake nucleation, yet it can slip seismically during dynamic weakening from a large throughgoing rupture.

Pensar en la intervención en crisis: Una propuesta desde intervenciones post desastres naturales de Chile y México

Living conditions in cities have brought opportunities and spaces for development, but they have also generated daily risks. Sometimes we are faced with natural events that have a devastation character. They can be, for example: fires, floods, as well as earthquakes, which are unpredictable and threatening. These situations are experienced by children with impotence, they feel helpless and incapable, hence the importance of proposing indications for psychological interventions in the face of catastrophic events. This work is fundamental for children to learn, firstly, to preserve themselves and help others and, secondly, to generate actions that allow them to mean these events, trying to learn about their capacities and this becomes a transforming experience for the development of cognitive strategies, as well as emotional resources. The objective will therefore be to prevent the experience from becoming traumatic. In this article we present the recovery of two intervention experiences with children, incorporating the dimension of the body symbolized towards expression via art and words and considering the axis of participation as a transversal theme in all intervention. It narrates the work with those children who suffered a great fire in Chile and then the experiences of earthquakes in Mexico.

Tsunami Modelling of the 8th September 2017 Mexico Earthquake of M 8.1, Using Two Different Software

On 8th of September 2017, an earthquake of magnitude Mw 8.1 was generated offshore Mexico, Chiapas area, at 04:49 UTC, with a depth of 72 km and the following coordinates: Latitude 15.02 N, Longitude 93.81 W, 98 km away from Pijijiapan (Mexico). The fault plane solution of the event was normal plane. Maximum tsunami waves of 1.1 m were measured at Salina Cruz sea level station, following the earthquake. Tsunami modelling simulations were accomplished using the earthquake’s parameters (location, magnitude, depth) and moment tensor solutions given by 3 different agencies: United States Geological Survey (USGS), German Research Centre for Geosciences (GFZ) and Global Centroid Moment Tensor (GCMT). For every case studied, the affected locations, sea level estimates and maximum wave heights were computed. There are two software used for modelling, the Tsunami Analysis Tool (TAT), provided and developed by the Joint Research Centre, Ispra, Italy and TRIDEC Cloud, provided by the German Research Centre for Geosciences (GFZ), Potsdam, Germany. After analysing the modelling scenarios, a comparison between the results of the two software was accomplished, for the same earthquake parameters. The results show that the parameters of GCMT computed with TAT overestimate those computed with TRIDEC, of maximum 3.9 m wave height at Arista with TAT and 2.46 m with TRIDEC. For the GFZ parameters, the estimates give 3.5 m for Pasito de la Senora with TAT, compared to 1.64 m maximum waves at Puerto Madero with TRIDEC. For the USGS data set, the results are similar, maximum waves of 2.4 m at Pasito de la Senora with TAT, and 2.9 m at Puerto Madero with TRIDEC. The Salina Cruz station, where 1.1 m height waves were measured, gives results only for the simulations ran with TAT, with 1.0 m for the GFZ earthquake parameters, 0.6 m for USGS and 1.4 m for the GCMT parameters.