EL DOCTOR OCTAVIO CASTANOS GARZA TOMO POSESION COMO DIRECTOR DEL INSTITUTO DE CIENCIAS NUCLEARES ... more EL DOCTOR OCTAVIO CASTANOS GARZA TOMO POSESION COMO DIRECTOR DEL INSTITUTO DE CIENCIAS NUCLEARES (ICN), EL 4 DE JUNIO, EN SUSTITUCION DEL DOCTOR MARCOS ROSENBAUM PITLUCK. EL DOCTOR GERARDO SUAREZ REYNOSO, COORDINADOR DE LA INVESTIGACION CIENTIFICA, FUE EL ENCARGADO DE DARLE POSESION DEL CARGO. SE ANOTAN DATOS CURRICULARES DEL NUEVO DIRECTOR Y DE LOS ORIGENES DEL ICN.
Bulletin of the Seismological Society of America, Dec 9, 2022
ABSTRACT Mexico City has sustained severe damage from earthquakes located in the subduction zone ... more ABSTRACT Mexico City has sustained severe damage from earthquakes located in the subduction zone and within the subducted Cocos plate. The city lies in the trans-Mexican volcanic belt (TMVB). Earthquakes in the TMVB are relatively infrequent but have reached Mw>6. A recent Mw 6.9 crustal earthquake occurred in 1912, 80 km from Mexico City. Damage scenarios are estimated for two hypothetical crustal earthquakes located 40 and 80 km from the city. The seismic sources represent hazard-critical earthquakes and are based on historical seismicity and on the geological record. The probability distribution of ground acceleration is determined by ground-motion models (GMMs) from similar tectonic regions. Site effects are included to account for the geotechnical zonation of the city, and vulnerability curves are calculated for residential buildings in the cadastral record of Mexico City. The results show that an earthquake near the 1912 earthquake would produce accelerations of 37 and 148 cm/s2 on firm ground and in the lake region, respectively. In this scenario, damage is concentrated in buildings 1-2 stories high located near the transition zone. The earthquake located ∼40 km from Mexico City shows accelerations of 79 and 318 cm/s2 on firm ground and in the lake region, respectively. This scenario concentrated potential damage in buildings 1-2 stories high and broadly distributed in the region underlain by soft clays. Under both scenarios, no damage is expected in buildings higher than ∼11 stories. A deterministic approach using two potential seismic sources instead of a probabilistic seismic hazard model is used because of the lack of background seismicity and the unknown recurrence times of events in the TMVB. The results show very different damage patterns for crustal earthquakes. The two scenarios presented here may be useful for decision makers and insurance companies to estimate physical damage and to implement mitigation programs.
Bulletin of the Seismological Society of America, Jul 10, 2018
A new seismic early warning algorithm is presented that estimates a magnitude threshold using the... more A new seismic early warning algorithm is presented that estimates a magnitude threshold using the first 3 s of the P-wave coda on the vertical component. The algorithm considerably reduces the processing time compared to previous algorithms used by the Mexican seismic early warning system (Seismic Alert System of Mexico [SASMEX]). It was designed to alert earthquakes within the subducted Cocos plate. The tP 3 algorithm was based on a training dataset of 76 accelerograms of 25 Mexican in-slab earthquakes, with focal depths > 40 km. The algorithm uses two parameters based on the unfiltered vertical component of the P waves: the sum of the cumulative quadratic acceleration, av T and θP a parameter that represents the slope of the cumulative acceleration. The model is based on a learning machine that linearizes piecewise the empirical relation between these two parameters and magnitude Mw. The resulting algorithm was tested on nine earthquakes that took place from 2014 to 2017, recorded in 37 strong-motion records. In addition, the algorithm was evaluated in the context of the Mexican earthquake early warning, applying it to 24 in-slab earthquakes occurring from 1995 to 2017 (5:0 < Mw < 7:1). The magnitude of 19 earthquakes was properly estimated; for four of them, it was overestimated and in one case the magnitude was underestimated. Three earthquakes Mw > 6:5 that affected Mexico City were included in the dataset: the Mw 6.5 event on 11 December 2011 and the destructive in-slab Tehuacán and Morelos earthquakes on 15 June 1999 (Mw 7.0) and 19 September 2017 (Mw 7.1). The retrospective application of the tP 3 algorithm shows that these three earthquakes are correctly identified as Mw > 6 and would activate a seismic alert. The tP 3 algorithm would have given an advance warning of 34, 35, and 16 s respectively, before the arrival of strong motion in Mexico City. Electronic Supplement: Tables showing the hypocentral data of the catalog of earthquakes and the results of the performance evaluation of the tP 3 algorithm on earthquakes within the subducted Cocos plate.
ABSTRACT A sequence of very strong earthquakes occurred from 28 March to 18 April, 1787. The firs... more ABSTRACT A sequence of very strong earthquakes occurred from 28 March to 18 April, 1787. The first earthquake on 28 March, appears to be the largest of the sequence followed by three strong events on 29 and 30 March, and 3 April; strong aftershocks continued to be reported until 18 April. The event of 28 March was strongly felt and caused damage in Mexico City, where several buildings were reported to suffer. The strongest effects, however, were observed on the southeastern coast of Guerrero and Oaxaca. Intensities greater than 8 (MMI) were observed along the coast over a distance of about 400 km. The towns of Ometepec, Jamiltepec and Tehuantepec reported strong damage to local churches and other apparently well-constructed buildings. In contrast to the low intensities observed during the coastal Oaxaca earthquakes of 1965, 1968 and 1978, Oaxaca City reports damage equivalent to intensity 8 to 9 on 28 March, 1787. An unusual effect of this earthquake on the Mexican subduction zone was the presence of a very large tsunami. Three different sources report that in the area known as the Barra de Alotengo (16.2N, 98.2 W) the sea retreated for a distance of about one Spanish league (4.1 km). A large wave came back and invaded land for approximately 1.5 leagues (6.2 km). Several local ranchers were swept away by the coming wave. Along the coast near the town of Tehuantepec, about 400 km to the southeast of Alotengo a tsunami was also reported to have stranded fish and shellfish inland; in this case no description of the distance penetrated by the tsunami is reported. It is also described that in Acapulco, some 200 km to the northwest of Alotengo, a strong wave was observed and that the sea remained agitated for a whole day. Assumming that the subduction zone ruptured from somewhere near Alotengo to the coast Tehuantepec, the resulting fault lenght is about 400 to 450 km. This large fault rupture contrasts with the seismic cycle of the Oaxaca coast observed during this century where apparently earthquakes with magnitudes Mw &gt; 7.4 ruptured asperities with a return period of about 32 to 56 years. The presence of a great earthquake rupturing approximately 450 km of the Mexican subduction zone with an equivalent magnitude of about 8.5 is a phenomenon not observed during instrumental times. The presence of such a large rupture process, as the one suspected on 28 March, 1787, raises the question whether great events like this one may take place in other segments of the Mexican subduction zone.
Bulletin of the Seismological Society of America, Dec 19, 2017
The tS–tP earthquake early warning algorithm measures the energy of the P-wave coda on the vertic... more The tS–tP earthquake early warning algorithm measures the energy of the P-wave coda on the vertical component in the tS–tP period to make a magnitude threshold estimation. The algorithm is based on two parameters: the logarithm of the peak ground acceleration, max a tS–tP and the logarithmic cumulative acceleration SA tS–tP . The model is built using a learning algorithm that iteratively parameterizes the linear fit of max a tS–tP and SA tS–tP to Mw in segments. Training datasets were based on 324 accelerograms from 101 earthquakes (4:8 ≤ Mw ≤ 8:1) in the Mexican subduction zone from 1985 to 2013. The algorithm is supervised to avoid outliers in the data. The process results in a family of linear equations parameterizing the observations to magnitude m tS–tP calibrated to the observedMw. The algorithm was successfully tested using a dataset of 28 earthquakes in the Mexican subduction zone, from 2014 to 2017. The performance of tS–tP algorithm was tested as a warning tool using 89 earthquakes in the Mexican subduction zone from 1985 to 2017, that met the criterion of having at least two stations within 70 km from the epicenter. The results show that 79 were correctly screened. The magnitude of six events was overestimated and four were underestimated. These earthquakes had an unfavorable station distribution. TheMw 6 South Napa, California, earthquake of 24 August 2014 was used also as a test case. The two closest stations identified it as Mw ≥5:8 within 2 s after the arrival of the P phase. This resulted in a lead time of 10 s in Berkeley and 12 s in San Francisco, prior to the arrival of the S waves. Thus, the tS–tP algorithm proves to be a reliable tool for seismic early warning where hypocenters are close to the target cities. Electronic Supplement: Earthquake catalog and table showing performance evaluation of the tS–tP algorithm.
EL DOCTOR OCTAVIO CASTANOS GARZA TOMO POSESION COMO DIRECTOR DEL INSTITUTO DE CIENCIAS NUCLEARES ... more EL DOCTOR OCTAVIO CASTANOS GARZA TOMO POSESION COMO DIRECTOR DEL INSTITUTO DE CIENCIAS NUCLEARES (ICN), EL 4 DE JUNIO, EN SUSTITUCION DEL DOCTOR MARCOS ROSENBAUM PITLUCK. EL DOCTOR GERARDO SUAREZ REYNOSO, COORDINADOR DE LA INVESTIGACION CIENTIFICA, FUE EL ENCARGADO DE DARLE POSESION DEL CARGO. SE ANOTAN DATOS CURRICULARES DEL NUEVO DIRECTOR Y DE LOS ORIGENES DEL ICN.
Bulletin of the Seismological Society of America, Dec 9, 2022
ABSTRACT Mexico City has sustained severe damage from earthquakes located in the subduction zone ... more ABSTRACT Mexico City has sustained severe damage from earthquakes located in the subduction zone and within the subducted Cocos plate. The city lies in the trans-Mexican volcanic belt (TMVB). Earthquakes in the TMVB are relatively infrequent but have reached Mw&gt;6. A recent Mw 6.9 crustal earthquake occurred in 1912, 80 km from Mexico City. Damage scenarios are estimated for two hypothetical crustal earthquakes located 40 and 80 km from the city. The seismic sources represent hazard-critical earthquakes and are based on historical seismicity and on the geological record. The probability distribution of ground acceleration is determined by ground-motion models (GMMs) from similar tectonic regions. Site effects are included to account for the geotechnical zonation of the city, and vulnerability curves are calculated for residential buildings in the cadastral record of Mexico City. The results show that an earthquake near the 1912 earthquake would produce accelerations of 37 and 148 cm/s2 on firm ground and in the lake region, respectively. In this scenario, damage is concentrated in buildings 1-2 stories high located near the transition zone. The earthquake located ∼40 km from Mexico City shows accelerations of 79 and 318 cm/s2 on firm ground and in the lake region, respectively. This scenario concentrated potential damage in buildings 1-2 stories high and broadly distributed in the region underlain by soft clays. Under both scenarios, no damage is expected in buildings higher than ∼11 stories. A deterministic approach using two potential seismic sources instead of a probabilistic seismic hazard model is used because of the lack of background seismicity and the unknown recurrence times of events in the TMVB. The results show very different damage patterns for crustal earthquakes. The two scenarios presented here may be useful for decision makers and insurance companies to estimate physical damage and to implement mitigation programs.
Bulletin of the Seismological Society of America, Jul 10, 2018
A new seismic early warning algorithm is presented that estimates a magnitude threshold using the... more A new seismic early warning algorithm is presented that estimates a magnitude threshold using the first 3 s of the P-wave coda on the vertical component. The algorithm considerably reduces the processing time compared to previous algorithms used by the Mexican seismic early warning system (Seismic Alert System of Mexico [SASMEX]). It was designed to alert earthquakes within the subducted Cocos plate. The tP 3 algorithm was based on a training dataset of 76 accelerograms of 25 Mexican in-slab earthquakes, with focal depths > 40 km. The algorithm uses two parameters based on the unfiltered vertical component of the P waves: the sum of the cumulative quadratic acceleration, av T and θP a parameter that represents the slope of the cumulative acceleration. The model is based on a learning machine that linearizes piecewise the empirical relation between these two parameters and magnitude Mw. The resulting algorithm was tested on nine earthquakes that took place from 2014 to 2017, recorded in 37 strong-motion records. In addition, the algorithm was evaluated in the context of the Mexican earthquake early warning, applying it to 24 in-slab earthquakes occurring from 1995 to 2017 (5:0 < Mw < 7:1). The magnitude of 19 earthquakes was properly estimated; for four of them, it was overestimated and in one case the magnitude was underestimated. Three earthquakes Mw > 6:5 that affected Mexico City were included in the dataset: the Mw 6.5 event on 11 December 2011 and the destructive in-slab Tehuacán and Morelos earthquakes on 15 June 1999 (Mw 7.0) and 19 September 2017 (Mw 7.1). The retrospective application of the tP 3 algorithm shows that these three earthquakes are correctly identified as Mw > 6 and would activate a seismic alert. The tP 3 algorithm would have given an advance warning of 34, 35, and 16 s respectively, before the arrival of strong motion in Mexico City. Electronic Supplement: Tables showing the hypocentral data of the catalog of earthquakes and the results of the performance evaluation of the tP 3 algorithm on earthquakes within the subducted Cocos plate.
ABSTRACT A sequence of very strong earthquakes occurred from 28 March to 18 April, 1787. The firs... more ABSTRACT A sequence of very strong earthquakes occurred from 28 March to 18 April, 1787. The first earthquake on 28 March, appears to be the largest of the sequence followed by three strong events on 29 and 30 March, and 3 April; strong aftershocks continued to be reported until 18 April. The event of 28 March was strongly felt and caused damage in Mexico City, where several buildings were reported to suffer. The strongest effects, however, were observed on the southeastern coast of Guerrero and Oaxaca. Intensities greater than 8 (MMI) were observed along the coast over a distance of about 400 km. The towns of Ometepec, Jamiltepec and Tehuantepec reported strong damage to local churches and other apparently well-constructed buildings. In contrast to the low intensities observed during the coastal Oaxaca earthquakes of 1965, 1968 and 1978, Oaxaca City reports damage equivalent to intensity 8 to 9 on 28 March, 1787. An unusual effect of this earthquake on the Mexican subduction zone was the presence of a very large tsunami. Three different sources report that in the area known as the Barra de Alotengo (16.2N, 98.2 W) the sea retreated for a distance of about one Spanish league (4.1 km). A large wave came back and invaded land for approximately 1.5 leagues (6.2 km). Several local ranchers were swept away by the coming wave. Along the coast near the town of Tehuantepec, about 400 km to the southeast of Alotengo a tsunami was also reported to have stranded fish and shellfish inland; in this case no description of the distance penetrated by the tsunami is reported. It is also described that in Acapulco, some 200 km to the northwest of Alotengo, a strong wave was observed and that the sea remained agitated for a whole day. Assumming that the subduction zone ruptured from somewhere near Alotengo to the coast Tehuantepec, the resulting fault lenght is about 400 to 450 km. This large fault rupture contrasts with the seismic cycle of the Oaxaca coast observed during this century where apparently earthquakes with magnitudes Mw &gt; 7.4 ruptured asperities with a return period of about 32 to 56 years. The presence of a great earthquake rupturing approximately 450 km of the Mexican subduction zone with an equivalent magnitude of about 8.5 is a phenomenon not observed during instrumental times. The presence of such a large rupture process, as the one suspected on 28 March, 1787, raises the question whether great events like this one may take place in other segments of the Mexican subduction zone.
Bulletin of the Seismological Society of America, Dec 19, 2017
The tS–tP earthquake early warning algorithm measures the energy of the P-wave coda on the vertic... more The tS–tP earthquake early warning algorithm measures the energy of the P-wave coda on the vertical component in the tS–tP period to make a magnitude threshold estimation. The algorithm is based on two parameters: the logarithm of the peak ground acceleration, max a tS–tP and the logarithmic cumulative acceleration SA tS–tP . The model is built using a learning algorithm that iteratively parameterizes the linear fit of max a tS–tP and SA tS–tP to Mw in segments. Training datasets were based on 324 accelerograms from 101 earthquakes (4:8 ≤ Mw ≤ 8:1) in the Mexican subduction zone from 1985 to 2013. The algorithm is supervised to avoid outliers in the data. The process results in a family of linear equations parameterizing the observations to magnitude m tS–tP calibrated to the observedMw. The algorithm was successfully tested using a dataset of 28 earthquakes in the Mexican subduction zone, from 2014 to 2017. The performance of tS–tP algorithm was tested as a warning tool using 89 earthquakes in the Mexican subduction zone from 1985 to 2017, that met the criterion of having at least two stations within 70 km from the epicenter. The results show that 79 were correctly screened. The magnitude of six events was overestimated and four were underestimated. These earthquakes had an unfavorable station distribution. TheMw 6 South Napa, California, earthquake of 24 August 2014 was used also as a test case. The two closest stations identified it as Mw ≥5:8 within 2 s after the arrival of the P phase. This resulted in a lead time of 10 s in Berkeley and 12 s in San Francisco, prior to the arrival of the S waves. Thus, the tS–tP algorithm proves to be a reliable tool for seismic early warning where hypocenters are close to the target cities. Electronic Supplement: Earthquake catalog and table showing performance evaluation of the tS–tP algorithm.
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