Gianfranco Vannucci, Paolo Gasperini, Laura Gulia, Barbara Lolli
Abstract We aim to compute macroseismic parameters (location and magnitude) using the BOXER code for the first time on the citizen testimonies, that is, individual intensity data points (IDPs) at the global scale collected and made available by the LastQuake system of the European–Mediterranean Seismological Centre (EMSC). IDPs available for different earthquakes are selected to eliminate those that are geographically inconsistent with most data; then they are clustered spatially based on various methods. For each cluster with at least three IDPs, a macroseismic data point (MDP), corresponding to an intensity value assessed for given localities as in classical macroseismic studies, is computed by various central tendency estimators (average, median, and trimmed averages). Finally, macroseismic parameters are obtained by MDP distribution using two location methods of BOXER code. For each earthquake, we used raw and corrected intensities and 132 different combinations of grouping methods, estimators, and BOXER methods. We assigned a ranking to the combinations that best reproduce instrumental parameters and used such a ranking to select preferred combinations for each earthquake. We analyzed retrospectively the reliability of the parameters as a function of time and space. The results are essentially identical using original and corrected intensities and show higher reliability for BOXER’s method 1 than for method 0; they are dependent on the geographical area, and generally improve over time and with the number of IDPs collected. These findings are useful for the future real-time analyses, and for evaluating the location and magnitude of earthquakes whenever a sufficient number of IDPs are available and with a distribution such that MDPs can be derived and the BOXER method applied.
{"title":"Earthquakes Parameters from Citizen Testimonies: A Retrospective Analysis of EMSC Database","authors":"Gianfranco Vannucci, Paolo Gasperini, Laura Gulia, Barbara Lolli","doi":"10.1785/0220230245","DOIUrl":"https://doi.org/10.1785/0220230245","url":null,"abstract":"Abstract We aim to compute macroseismic parameters (location and magnitude) using the BOXER code for the first time on the citizen testimonies, that is, individual intensity data points (IDPs) at the global scale collected and made available by the LastQuake system of the European–Mediterranean Seismological Centre (EMSC). IDPs available for different earthquakes are selected to eliminate those that are geographically inconsistent with most data; then they are clustered spatially based on various methods. For each cluster with at least three IDPs, a macroseismic data point (MDP), corresponding to an intensity value assessed for given localities as in classical macroseismic studies, is computed by various central tendency estimators (average, median, and trimmed averages). Finally, macroseismic parameters are obtained by MDP distribution using two location methods of BOXER code. For each earthquake, we used raw and corrected intensities and 132 different combinations of grouping methods, estimators, and BOXER methods. We assigned a ranking to the combinations that best reproduce instrumental parameters and used such a ranking to select preferred combinations for each earthquake. We analyzed retrospectively the reliability of the parameters as a function of time and space. The results are essentially identical using original and corrected intensities and show higher reliability for BOXER’s method 1 than for method 0; they are dependent on the geographical area, and generally improve over time and with the number of IDPs collected. These findings are useful for the future real-time analyses, and for evaluating the location and magnitude of earthquakes whenever a sufficient number of IDPs are available and with a distribution such that MDPs can be derived and the BOXER method applied.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":"44 5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136068343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kiran Kumar Singh Thingbaijam, Mark S. Rattenbury, Russ J. Van Dissen, Matt C. Gerstenberger, John Ristau, Delphine D. Fitzenz
Abstract Applying distributed seismicity models for seismic hazard analysis requires postulating the styles of faulting and nodal planes for anticipated earthquakes. Here, we present a model describing focal mechanisms, or more specifically, strike, dip, and rake angles, for the ruptures of shallow (hypocentral depth ≤40 km) crustal earthquakes in Aotearoa New Zealand. This model is based on delineations of neotectonic domains and analysis of pre-existing datasets, including an active fault database, geological map-based fault datasets, the New Zealand Community Fault Model, and a regional moment tensor catalog. We demonstrate that the focal mechanism model is broadly consistent with the regional moment tensor catalog, with respect to spatial distributions of P and T axes and in terms of the Kagan angle. This characterization of focal mechanisms complements the distributed seismicity component of the New Zealand National Seismic Hazard Model 2022.
{"title":"Characterization of Focal Mechanisms for Upper Crustal Distributed Seismicity in Aotearoa New Zealand","authors":"Kiran Kumar Singh Thingbaijam, Mark S. Rattenbury, Russ J. Van Dissen, Matt C. Gerstenberger, John Ristau, Delphine D. Fitzenz","doi":"10.1785/0220230196","DOIUrl":"https://doi.org/10.1785/0220230196","url":null,"abstract":"Abstract Applying distributed seismicity models for seismic hazard analysis requires postulating the styles of faulting and nodal planes for anticipated earthquakes. Here, we present a model describing focal mechanisms, or more specifically, strike, dip, and rake angles, for the ruptures of shallow (hypocentral depth ≤40 km) crustal earthquakes in Aotearoa New Zealand. This model is based on delineations of neotectonic domains and analysis of pre-existing datasets, including an active fault database, geological map-based fault datasets, the New Zealand Community Fault Model, and a regional moment tensor catalog. We demonstrate that the focal mechanism model is broadly consistent with the regional moment tensor catalog, with respect to spatial distributions of P and T axes and in terms of the Kagan angle. This characterization of focal mechanisms complements the distributed seismicity component of the New Zealand National Seismic Hazard Model 2022.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136382177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Célia Marreiros, Paulo M. Alves, Susana Custódio, Carlos S. Oliveira, Fernando Carrilho
Abstract On 28 February 1969, an Mw 7.8 earthquake occurred 180 km southwest of Cape Saint Vincent, Portugal. The earthquake was widely felt in mainland Portugal, Madeira Island, Spain, Morocco, and even as far as Andorra and France, reaching a maximum intensity of VIII in the south of Portugal. In 2019, on the 50th anniversary of the earthquake, there was launched online an international “Did You Feel It 50 Years Ago?” (DYFI-50y) survey, published in several languages, for citizens to report the observed effects of the earthquake. This initiative had two main purposes: first, to collect and preserve community observations of the earthquake; and second, to test the online implementation of the DYFI questionnaire at Instituto Português do Mar e da Atmosfera for a damaging event. The DYFI-50y questionnaire was disseminated widely in the media, and a school project was launched for school-age children to collect reports from grandparents or other close elders. In total, more than 3000 reports were collected, a number that is close to the number of reports received for a recent M 6 earthquake in 2009. The collected community reports provide good coverage of mainland Portugal, particularly in Lisbon and Porto’s densely populated urban centers. In low-population areas, the limited results do not allow for robust statistics, and variability becomes significant. The distribution of intensities obtained shows a generally good agreement with other sources, indicating that the community reports are reliable and complement existing intensity maps for this earthquake, further clarifying some of the observed patterns. It was concluded that an online questionnaire is an efficient tool for gathering data several years after the earthquake.
1969年2月28日，葡萄牙圣文森特角西南180公里处发生里氏7.8级地震。葡萄牙本土、马德拉岛、西班牙、摩洛哥等地均有震感，甚至远至安道尔和法国，葡萄牙南部最高震级达8级。2019年，在地震50周年之际，网上发起了一项国际活动“50年前你感受到了吗?”(DYFI-50y)的调查报告，以几种语言出版，供市民报告观察到的地震影响。这一举措有两个主要目的:首先，收集和保存社区对地震的观察;第二，在Instituto Português do Mar e da Atmosfera上测试DYFI调查问卷的在线实施情况，以应对破坏性事件。DYFI-50y调查问卷在媒体上广泛传播，并发起了一项针对学龄儿童的学校项目，收集祖父母或其他亲密长者的报告。总共收集了3000多份报告，这个数字接近2009年最近一次6级地震收到的报告数量。收集的社区报告很好地覆盖了葡萄牙大陆，特别是在里斯本和波尔图人口稠密的城市中心。在人口稀少的地区，有限的结果不允许可靠的统计，变异性变得显著。获得的强度分布与其他来源大体一致，表明社区报告是可靠的，并补充了现有的地震强度图，进一步澄清了一些观察到的模式。结论是，在地震发生几年后，在线问卷是收集数据的有效工具。
{"title":"“Did You Feel It 50 Years Ago?” The 1969 Mw 7.8 Cape Saint Vincent Earthquake","authors":"Célia Marreiros, Paulo M. Alves, Susana Custódio, Carlos S. Oliveira, Fernando Carrilho","doi":"10.1785/0220230191","DOIUrl":"https://doi.org/10.1785/0220230191","url":null,"abstract":"Abstract On 28 February 1969, an Mw 7.8 earthquake occurred 180 km southwest of Cape Saint Vincent, Portugal. The earthquake was widely felt in mainland Portugal, Madeira Island, Spain, Morocco, and even as far as Andorra and France, reaching a maximum intensity of VIII in the south of Portugal. In 2019, on the 50th anniversary of the earthquake, there was launched online an international “Did You Feel It 50 Years Ago?” (DYFI-50y) survey, published in several languages, for citizens to report the observed effects of the earthquake. This initiative had two main purposes: first, to collect and preserve community observations of the earthquake; and second, to test the online implementation of the DYFI questionnaire at Instituto Português do Mar e da Atmosfera for a damaging event. The DYFI-50y questionnaire was disseminated widely in the media, and a school project was launched for school-age children to collect reports from grandparents or other close elders. In total, more than 3000 reports were collected, a number that is close to the number of reports received for a recent M 6 earthquake in 2009. The collected community reports provide good coverage of mainland Portugal, particularly in Lisbon and Porto’s densely populated urban centers. In low-population areas, the limited results do not allow for robust statistics, and variability becomes significant. The distribution of intensities obtained shows a generally good agreement with other sources, indicating that the community reports are reliable and complement existing intensity maps for this earthquake, further clarifying some of the observed patterns. It was concluded that an online questionnaire is an efficient tool for gathering data several years after the earthquake.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135267478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mariagrazia De Caro, Caterina Montuori, Francesco Frugoni, Stephen Monna, Alessandra Giuntini
Abstract The Algerian offshore earthquake of 18 March 2021, Mw 6.0, was felt by people in various Italian regions, also at large epicentral distance. This unusual human perception far from the source prompted us to analyze the waveforms recorded by land seismic stations installed along the Iberian, French, and Italian coasts. On some seismograms of the selected network, prominent T phases are detected. T waves can travel in the SOund Fixing And Ranging (SOFAR) channel over great distances (thousands of kilometers) with little loss in signal strength and be recorded by near-coastal seismometers after the P (primary) and S (secondary) phases (hence T or tertiary phases). To explain the subjective perception of ground shaking with quantities that are measured on the seismogram, we estimated the empirical macroseismic intensities for both body and T phases and we calculated the body-wave seismic attenuation. The P-wave anelastic attenuation analysis shows two main wave propagation patterns that reflect lithosphere heterogeneity of the Algerian, Liguro-Provençal, and Tyrrhenian basins. We find that in some cases, in particular along the Italian and French coasts, the largest ground shaking is caused by the T phase. Our observations confirm that the central-western Mediterranean Sea is a favorable site for T-wave propagation and suggest that the T phases should be taken into account in ground-shaking hazard assessment for the central-western Mediterranean.
{"title":"Seismic <i>T</i> Phases in the Western-Central Mediterranean: Source of Seismic Hazard?","authors":"Mariagrazia De Caro, Caterina Montuori, Francesco Frugoni, Stephen Monna, Alessandra Giuntini","doi":"10.1785/0220220326","DOIUrl":"https://doi.org/10.1785/0220220326","url":null,"abstract":"Abstract The Algerian offshore earthquake of 18 March 2021, Mw 6.0, was felt by people in various Italian regions, also at large epicentral distance. This unusual human perception far from the source prompted us to analyze the waveforms recorded by land seismic stations installed along the Iberian, French, and Italian coasts. On some seismograms of the selected network, prominent T phases are detected. T waves can travel in the SOund Fixing And Ranging (SOFAR) channel over great distances (thousands of kilometers) with little loss in signal strength and be recorded by near-coastal seismometers after the P (primary) and S (secondary) phases (hence T or tertiary phases). To explain the subjective perception of ground shaking with quantities that are measured on the seismogram, we estimated the empirical macroseismic intensities for both body and T phases and we calculated the body-wave seismic attenuation. The P-wave anelastic attenuation analysis shows two main wave propagation patterns that reflect lithosphere heterogeneity of the Algerian, Liguro-Provençal, and Tyrrhenian basins. We find that in some cases, in particular along the Italian and French coasts, the largest ground shaking is caused by the T phase. Our observations confirm that the central-western Mediterranean Sea is a favorable site for T-wave propagation and suggest that the T phases should be taken into account in ground-shaking hazard assessment for the central-western Mediterranean.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135273262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nicolas Harrichhausen, Laurence Audin, Stéphane Baize, Kendra L. Johnson, Céline Beauval, Paul Jarrin, Léo Marconato, Frédérique Rolandone, Hervé Jomard, Jean-Mathieu Nocquet, Alexandra Alvarado, Patricia A. Mothes
Abstract We explore how variation of slip rates in fault source models affect computed earthquake rates of the Pallatanga–Puna fault system in Ecuador. Determining which slip rates best represent fault-zone seismicity is vital for use in probabilistic seismic hazard assessment (PSHA). However, given the variable spatial and temporal scales slip rates are measured over, significantly different rates can be observed along the same fault. The Pallatanga–Puna fault in southern Ecuador exemplifies a fault where different slip rates have been measured using methods spanning different spatial and temporal scales, and in which historical data and paleoseismic studies provide a record of large earthquakes over a relatively long time span. We use fault source models to calculate earthquake rates using different slip rates and geometries for the Pallatanga–Puna fault, and compare the computed magnitude–frequency distributions (MFDs) to earthquake catalog MFDs from the fault zone. We show that slip rates measured across the entire width of the fault zone, either based on geodesy or long-term geomorphic offsets, produce computed MFDs that compare more favorably with the catalog data. Moreover, we show that the computed MFDs fit the earthquake catalog data best when they follow a hybrid-characteristic MFD shape. These results support hypotheses that slip rates derived from a single fault strand of a fault system do not represent seismicity produced by the entire fault zone.
{"title":"Fault Source Models Show Slip Rates Measured across the Width of the Entire Fault Zone Best Represent the Observed Seismicity of the Pallatanga–Puna Fault, Ecuador","authors":"Nicolas Harrichhausen, Laurence Audin, Stéphane Baize, Kendra L. Johnson, Céline Beauval, Paul Jarrin, Léo Marconato, Frédérique Rolandone, Hervé Jomard, Jean-Mathieu Nocquet, Alexandra Alvarado, Patricia A. Mothes","doi":"10.1785/0220230217","DOIUrl":"https://doi.org/10.1785/0220230217","url":null,"abstract":"Abstract We explore how variation of slip rates in fault source models affect computed earthquake rates of the Pallatanga–Puna fault system in Ecuador. Determining which slip rates best represent fault-zone seismicity is vital for use in probabilistic seismic hazard assessment (PSHA). However, given the variable spatial and temporal scales slip rates are measured over, significantly different rates can be observed along the same fault. The Pallatanga–Puna fault in southern Ecuador exemplifies a fault where different slip rates have been measured using methods spanning different spatial and temporal scales, and in which historical data and paleoseismic studies provide a record of large earthquakes over a relatively long time span. We use fault source models to calculate earthquake rates using different slip rates and geometries for the Pallatanga–Puna fault, and compare the computed magnitude–frequency distributions (MFDs) to earthquake catalog MFDs from the fault zone. We show that slip rates measured across the entire width of the fault zone, either based on geodesy or long-term geomorphic offsets, produce computed MFDs that compare more favorably with the catalog data. Moreover, we show that the computed MFDs fit the earthquake catalog data best when they follow a hybrid-characteristic MFD shape. These results support hypotheses that slip rates derived from a single fault strand of a fault system do not represent seismicity produced by the entire fault zone.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":"2004 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135273070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Seismic waves induced by incident acoustic waves from air disturbances can be used to image near-surface structures. In this article, we analyze seismic waveforms recorded by a dense array on the Xishancun landside in Li County, Sichuan Province, southwest China during the Lunar New Year’s Eve (27 January 2017). A total of eight event clusters have been identified as a result of firework explosions. For each cluster, which comprises dozens of individual events with high similarity, we manually pick arrival times of the first event recorded by the array and locate it with a grid-search method. We then rotate three-component waveforms of all events from the east, north, and vertical coordinate system to the local LQT coordinates (L, positive direction perpendicular to the landslide surface and pointing downwards; Q, positive direction is from the launch location of firework to the station along the landslide surface; T, perpendicular to the plane formed by the L and Q directions, and the selected positive direction of the T axis makes LQT form the left-hand coordinate system), and stack the LQT components for those events with cross-correlation values CC ≥ 0.8 with respect to the first event. Characteristics of the stacked LQT components are also examined. The particle motions at each station are retrograde ellipse in the frequency range of ∼5–50 Hz, suggesting air-coupled Rayleigh waves generated by the firework explosions. Spectrograms of the Rayleigh waves also show clear dispersions, which might be used to image near-surface velocity structures. Although we cannot directly extract the phase velocities due to the limitation of the seismic array, our study shows that the fireworks might provide a low-cost and easy-to-use seismic source for imaging near-surface structures.
{"title":"Fireworks: A Potential Artificial Source for Imaging Near-Surface Structures","authors":"Risheng Chu, Qingdong Wang, Zhigang Peng, Minhan Sheng, Qiaoxia Liu, Haopeng Chen","doi":"10.1785/0220220281","DOIUrl":"https://doi.org/10.1785/0220220281","url":null,"abstract":"Abstract Seismic waves induced by incident acoustic waves from air disturbances can be used to image near-surface structures. In this article, we analyze seismic waveforms recorded by a dense array on the Xishancun landside in Li County, Sichuan Province, southwest China during the Lunar New Year’s Eve (27 January 2017). A total of eight event clusters have been identified as a result of firework explosions. For each cluster, which comprises dozens of individual events with high similarity, we manually pick arrival times of the first event recorded by the array and locate it with a grid-search method. We then rotate three-component waveforms of all events from the east, north, and vertical coordinate system to the local LQT coordinates (L, positive direction perpendicular to the landslide surface and pointing downwards; Q, positive direction is from the launch location of firework to the station along the landslide surface; T, perpendicular to the plane formed by the L and Q directions, and the selected positive direction of the T axis makes LQT form the left-hand coordinate system), and stack the LQT components for those events with cross-correlation values CC ≥ 0.8 with respect to the first event. Characteristics of the stacked LQT components are also examined. The particle motions at each station are retrograde ellipse in the frequency range of ∼5–50 Hz, suggesting air-coupled Rayleigh waves generated by the firework explosions. Spectrograms of the Rayleigh waves also show clear dispersions, which might be used to image near-surface velocity structures. Although we cannot directly extract the phase velocities due to the limitation of the seismic array, our study shows that the fireworks might provide a low-cost and easy-to-use seismic source for imaging near-surface structures.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135569412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alessandro Damiani, Valerio Poggi, Chiara Scaini, Mohsen Kohrangi, Paolo Bazzurro
Abstract Understanding the potential socioeconomic losses due to natural hazards, such as earthquakes, is of foremost importance in the field of catastrophe risk management. The construction of a probabilistic seismic risk model is complex and requires the tuning of several parameters essential to represent the seismic hazard of the region, the definition of the exposed inventory characteristics, and its vulnerability to ground motion. Because significant uncertainties could be associated with each model component, the loss estimates are often highly volatile. Nevertheless, to reduce the conceptual complexity and the computational burden, in many real-life applications these uncertainties are either not adequately treated or neglected altogether. The false high fidelity of the ensuing loss estimates can mislead decision-making strategies. Hence, it is useful to assess the influence that the variability in the estimated values of the model input parameters may exert on the final risk results and their relevant contributions. To this purpose, we have performed a sensitivity analysis of the results of an urban seismic risk assessment for Isfahan (Iran). Systematic variations have been applied to the values of the parameters that control the earthquake occurrence in the probabilistic seismic hazard model. Curves of input–output relative variations were built for different risk metrics with the goal of identifying the parameters most sensitive to input uncertainty. Our findings can be useful to support risk managers and practitioners in the process of building seismic hazard and risk models. We found that the Gutenberg–Richter a and b values, the maximum magnitude, and the threshold magnitude are large contributors to the variability of important risk measures, such as the 475 yr and the average annual loss, with the more frequent losses being, in general, most sensitive.
{"title":"Impact of the Uncertainty in the Parameters of the Earthquake Occurrence Model on Loss Estimates of Urban Building Portfolios","authors":"Alessandro Damiani, Valerio Poggi, Chiara Scaini, Mohsen Kohrangi, Paolo Bazzurro","doi":"10.1785/0220230248","DOIUrl":"https://doi.org/10.1785/0220230248","url":null,"abstract":"Abstract Understanding the potential socioeconomic losses due to natural hazards, such as earthquakes, is of foremost importance in the field of catastrophe risk management. The construction of a probabilistic seismic risk model is complex and requires the tuning of several parameters essential to represent the seismic hazard of the region, the definition of the exposed inventory characteristics, and its vulnerability to ground motion. Because significant uncertainties could be associated with each model component, the loss estimates are often highly volatile. Nevertheless, to reduce the conceptual complexity and the computational burden, in many real-life applications these uncertainties are either not adequately treated or neglected altogether. The false high fidelity of the ensuing loss estimates can mislead decision-making strategies. Hence, it is useful to assess the influence that the variability in the estimated values of the model input parameters may exert on the final risk results and their relevant contributions. To this purpose, we have performed a sensitivity analysis of the results of an urban seismic risk assessment for Isfahan (Iran). Systematic variations have been applied to the values of the parameters that control the earthquake occurrence in the probabilistic seismic hazard model. Curves of input–output relative variations were built for different risk metrics with the goal of identifying the parameters most sensitive to input uncertainty. Our findings can be useful to support risk managers and practitioners in the process of building seismic hazard and risk models. We found that the Gutenberg–Richter a and b values, the maximum magnitude, and the threshold magnitude are large contributors to the variability of important risk measures, such as the 475 yr and the average annual loss, with the more frequent losses being, in general, most sensitive.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135569266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shri Krishna Singh, Raúl Daniel Corona-Fernandez, Miguel Ángel Santoyo, Arturo Iglesias
Abstract Repeating large earthquakes (M ≥ 7), waveforms for which are nearly identical, have been identified only on the Mexican subduction thrust near Acapulco. These earthquakes occurred on 1962 (Ms 7.0) and 2021 (Ms 7.0, Mw 7.0). Here, we report on two more sequences of three repeating large earthquakes each in eastern and western Oaxaca, Mexico. The repeating earthquakes in eastern Oaxaca occurred on 23 March 1928 (Ms 7.5), 1965 (Ms 7.6, Mw 7.5), and 2020 (Ms 7.4, Mw 7.4), and in western Oaxaca on 4 August 1928 (Ms 7.4), 1968 (Ms 7.2, Mw 7.3), and 2018 (Ms 7.2, Mw 7.2). Galitzin seismograms of the earthquakes in each sequence at DeBilt, The Netherlands or at Strasbourg, France are strikingly similar for at least 2600 s after the P-wave arrival. Similarity of waveforms of earthquakes in each sequence and tests with seismograms of events locations for which are accurately known suggest that their source areas were less than 10–20 km of each other. Moment-rate functions of these events are remarkably simple. We also document quasi-repeating earthquakes in central Oaxaca on 17 June 1928 (Ms 7.6) and 29 November 1978 (Ms 7.6, Mw 7.6). Such events have similar locations with large overlap in primary slip but are not identical. Recently, Michoacán–Colima earthquakes of 1973 (Ms 7.5, Mw 7.6) and 2022 (Ms 7.6, Mw 7.6) were reported as quasi-repeaters. Repeating or quasi-repeating large earthquakes imply that they are known for all the other events in the sequence if we know the location and gross source parameters of one of them. This permits the estimation of recurrence periods and the delineation of seismic gaps with greater confidence. Repeating and quasi-repeating large earthquakes in Oaxaca, an unique observation, shed new light on seismic hazard of the region, provide further support for the characteristic earthquake model, and reveal remarkably persistent behavior of ruptures through multiple earthquake cycles.
{"title":"Repeating Large Earthquakes along the Mexican Subduction Zone","authors":"Shri Krishna Singh, Raúl Daniel Corona-Fernandez, Miguel Ángel Santoyo, Arturo Iglesias","doi":"10.1785/0220230243","DOIUrl":"https://doi.org/10.1785/0220230243","url":null,"abstract":"Abstract Repeating large earthquakes (M ≥ 7), waveforms for which are nearly identical, have been identified only on the Mexican subduction thrust near Acapulco. These earthquakes occurred on 1962 (Ms 7.0) and 2021 (Ms 7.0, Mw 7.0). Here, we report on two more sequences of three repeating large earthquakes each in eastern and western Oaxaca, Mexico. The repeating earthquakes in eastern Oaxaca occurred on 23 March 1928 (Ms 7.5), 1965 (Ms 7.6, Mw 7.5), and 2020 (Ms 7.4, Mw 7.4), and in western Oaxaca on 4 August 1928 (Ms 7.4), 1968 (Ms 7.2, Mw 7.3), and 2018 (Ms 7.2, Mw 7.2). Galitzin seismograms of the earthquakes in each sequence at DeBilt, The Netherlands or at Strasbourg, France are strikingly similar for at least 2600 s after the P-wave arrival. Similarity of waveforms of earthquakes in each sequence and tests with seismograms of events locations for which are accurately known suggest that their source areas were less than 10–20 km of each other. Moment-rate functions of these events are remarkably simple. We also document quasi-repeating earthquakes in central Oaxaca on 17 June 1928 (Ms 7.6) and 29 November 1978 (Ms 7.6, Mw 7.6). Such events have similar locations with large overlap in primary slip but are not identical. Recently, Michoacán–Colima earthquakes of 1973 (Ms 7.5, Mw 7.6) and 2022 (Ms 7.6, Mw 7.6) were reported as quasi-repeaters. Repeating or quasi-repeating large earthquakes imply that they are known for all the other events in the sequence if we know the location and gross source parameters of one of them. This permits the estimation of recurrence periods and the delineation of seismic gaps with greater confidence. Repeating and quasi-repeating large earthquakes in Oaxaca, an unique observation, shed new light on seismic hazard of the region, provide further support for the characteristic earthquake model, and reveal remarkably persistent behavior of ruptures through multiple earthquake cycles.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135570122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yiyu Ni, Marine A. Denolle, Rob Fatland, Naomi Alterman, Bradley P. Lipovsky, Friedrich Knuth
Abstract Large-scale processing and dissemination of distributed acoustic sensing (DAS) data are among the greatest computational challenges and opportunities of seismological research today. Current data formats and computing infrastructure are not well-adapted or user-friendly for large-scale processing. We propose an innovative, cloud-native solution for DAS seismology using the MinIO open-source object storage framework. We develop data schema for cloud-optimized data formats—Zarr and TileDB, which we deploy on a local object storage service compatible with the Amazon Web Services (AWS) storage system. We benchmark reading and writing performance for various data schema using canonical use cases in seismology. We test our framework on a local server and AWS. We find much-improved performance in compute time and memory throughout when using TileDB and Zarr compared to the conventional HDF5 data format. We demonstrate the platform with a computing heavy use case in seismology: ambient noise seismology of DAS data. We process one month of data, pairing all 2089 channels within 24 hr using AWS Batch autoscaling.
分布式声传感(DAS)数据的大规模处理和传播是当今地震研究中最大的计算挑战和机遇之一。当前的数据格式和计算基础设施不能很好地适应大规模处理或对用户友好。我们使用MinIO开源对象存储框架为DAS地震学提出了一种创新的云原生解决方案。我们为云优化的数据格式——zarr和TileDB开发了数据模式，并将其部署在与Amazon Web Services (AWS)存储系统兼容的本地对象存储服务上。我们使用地震学中的规范用例对各种数据模式的读写性能进行基准测试。我们在本地服务器和AWS上测试我们的框架。我们发现，与传统的HDF5数据格式相比，使用TileDB和Zarr在计算时间和内存方面有了很大的提高。我们用一个计算量大的地震学用例来演示该平台:DAS数据的环境噪声地震学。我们处理一个月的数据，使用AWS批处理自动缩放在24小时内配对所有2089个通道。
{"title":"An Object Storage for Distributed Acoustic Sensing","authors":"Yiyu Ni, Marine A. Denolle, Rob Fatland, Naomi Alterman, Bradley P. Lipovsky, Friedrich Knuth","doi":"10.1785/0220230172","DOIUrl":"https://doi.org/10.1785/0220230172","url":null,"abstract":"Abstract Large-scale processing and dissemination of distributed acoustic sensing (DAS) data are among the greatest computational challenges and opportunities of seismological research today. Current data formats and computing infrastructure are not well-adapted or user-friendly for large-scale processing. We propose an innovative, cloud-native solution for DAS seismology using the MinIO open-source object storage framework. We develop data schema for cloud-optimized data formats—Zarr and TileDB, which we deploy on a local object storage service compatible with the Amazon Web Services (AWS) storage system. We benchmark reading and writing performance for various data schema using canonical use cases in seismology. We test our framework on a local server and AWS. We find much-improved performance in compute time and memory throughout when using TileDB and Zarr compared to the conventional HDF5 data format. We demonstrate the platform with a computing heavy use case in seismology: ambient noise seismology of DAS data. We process one month of data, pairing all 2089 channels within 24 hr using AWS Batch autoscaling.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135569410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jenna L. Faith, Marianne S. Karplus, Stephen A. Veitch, Diane I. Doser, Alexandros Savvaidis
Abstract With increasing earthquakes in the Delaware basin since 2009, earthquake studies, including accurate hypocenters, are critically needed in the Delaware basin to identify the structures producing earthquakes, and to determine if they are related to unconventional petroleum development and production. In 2018, with funding from the Texas Seismological Network, we deployed and maintained a nodal network of 25 Magseis Fairfield Z-Land Generation 2 5-Hz seismic nodes in the Pecos, Texas, region of the Delaware basin, known as, The Pecos Array. The network was deployed from November 2018 to the beginning of January 2020, with an additional two months of data recorded in September and October 2020. The network collected continuous three-component data with a 1000-Hz sampling rate. The spacing of the nodes varied from ∼2 km in town to ∼10 km farther away from the city center. The primary goal of this network was to improve estimation of event hypocenters, which will help to determine why there has been an increase in earthquakes over the past several years. In this article, we summarize the scientific motivation, deployment details, and data quality of this network. Data quality statistics show that we successfully collected continuous data with signal-to-noise ratios that allow us to detect and locate events, hundreds of them being estimated at ML<0.50. This unique dataset is contributing to new seismotectonic studies in the Delaware basin.
{"title":"The Pecos Array: A Temporary Nodal Seismic Experiment in the Pecos, Texas, Region of the Delaware Basin","authors":"Jenna L. Faith, Marianne S. Karplus, Stephen A. Veitch, Diane I. Doser, Alexandros Savvaidis","doi":"10.1785/0220230108","DOIUrl":"https://doi.org/10.1785/0220230108","url":null,"abstract":"Abstract With increasing earthquakes in the Delaware basin since 2009, earthquake studies, including accurate hypocenters, are critically needed in the Delaware basin to identify the structures producing earthquakes, and to determine if they are related to unconventional petroleum development and production. In 2018, with funding from the Texas Seismological Network, we deployed and maintained a nodal network of 25 Magseis Fairfield Z-Land Generation 2 5-Hz seismic nodes in the Pecos, Texas, region of the Delaware basin, known as, The Pecos Array. The network was deployed from November 2018 to the beginning of January 2020, with an additional two months of data recorded in September and October 2020. The network collected continuous three-component data with a 1000-Hz sampling rate. The spacing of the nodes varied from ∼2 km in town to ∼10 km farther away from the city center. The primary goal of this network was to improve estimation of event hypocenters, which will help to determine why there has been an increase in earthquakes over the past several years. In this article, we summarize the scientific motivation, deployment details, and data quality of this network. Data quality statistics show that we successfully collected continuous data with signal-to-noise ratios that allow us to detect and locate events, hundreds of them being estimated at ML&lt;0.50. This unique dataset is contributing to new seismotectonic studies in the Delaware basin.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135778811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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