We present a high-resolution seismic catalog for the 2021 M_(S)6.4/M_(W)6.1 Yangbi sequence.The catalog has a time range of 2021-05-01 to 2021-05-28,and contains~8,000 well located events.It captures the features of t...We present a high-resolution seismic catalog for the 2021 M_(S)6.4/M_(W)6.1 Yangbi sequence.The catalog has a time range of 2021-05-01 to 2021-05-28,and contains~8,000 well located events.It captures the features of the whole foreshock sequence and the early aftershocks.We designed a detection strategy incorporating both an artificial intelligent(AI)picker and a matched filter algorithm.Here,we adopt a hybrid AI method incorporating convolutional and recurrent neural network(CNN&RNN)for event detection and phase picking respectively(i.e.CERP),a light-weight AI picker that can be trained with small volume of data.CERP is first trained with detections from a STA/LTA and Kurtosis-based method called PAL,and then construct a rather complete template set of~4,000 events.Finally,the matched filter algorithm MESS augments the initial detections and measures differential travel times with cross-correlation,which finally results in precise relocation.This process gives 9,026 detections,among which 7,943 events can be well relocated.The catalog shows as expected power-law distribution of frequency magnitude and reveals detailed pattern of seismicity evolution.The main features are:(1)the foreshock sequence images simple fault geometry with consistent strike,but also show a variable event depth along strike;(2)the mainshock ruptures the same fault of the foreshock sequence and activate conjugate faults further to the southeast;(3)complex seismicity are developed in the post-seismic period,indicating complex triggering mechanisms.Thus,our catalog provides a reliable basis for further investigations,such as b-value studies,rupture process,and triggering relations.展开更多
West Africa is considered a region of low seismicity. However, the monitoring of earthquake activity by local seismic arrays began very early (as early as 1914) in West Africa but seismic catalogs are very incomplete....West Africa is considered a region of low seismicity. However, the monitoring of earthquake activity by local seismic arrays began very early (as early as 1914) in West Africa but seismic catalogs are very incomplete. In 1991, Bertil studied the seismicity of West Africa based on networks of seismic stations in Ivory Coast and neighboring countries. The reference work of Ambraseys and Adams as well as the recent earthquakes given by the international data centres on the seismicity of West Africa were also used for the computations of earthquake hazard parameters. Different earthquake event data have been compiled and homogenised to moment magnitude (</span><i><span style="font-family:Verdana;">M</span><sub><span style="font-family:Verdana;">w</span></sub></i><span style="font-family:Verdana;">). The obtained catalog covers a period of over four centuries (1615-2021) and contains large historical events and recent complete observations. The complete catalog part has been subdivided into four complete subcatalogs with each a level of completeness. The minimum magnitude and the maximum observed magnitude are equal to 2.89 and 6.8 respectively for the whole catalog. The seismic code software developed by Kijko was used to calculate the earthquake hazard parameters. The results give a </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">b</span></i></span></span><span><span><span> </span></span></span><span><span><span><span style="font-family:Verdana;">value of 0.83 ± 0.08 for the whole period and preliminary seismic hazards curves are also plotted for re</span><span style="font-family:Verdana;">turn periods 25, 50 and 100 years. This is a good and practical example</span><span style="font-family:Verdana;"> showing that this procedure can be used for seismic hazard assessment in West Africa.展开更多
The analysis of seismic hazards relies on the statistical analysis of historical seismic data and the instrumental seismic catalog to obtain the regional earthquake recurrence interval and earthquake probability.The a...The analysis of seismic hazards relies on the statistical analysis of historical seismic data and the instrumental seismic catalog to obtain the regional earthquake recurrence interval and earthquake probability.The accuracy of analysis thus depends strongly on the completeness of the seismic data used.However,available seismic catalogs are too short or incomplete for the reliable analysis of the statistical characteristics of earthquakes.If a long-term synthetic seismic catalog can be generated using a physics-based numerical simulation,and the simulation results match the crustal deformation,seismicity,and other observations,then such a synthetic catalog helps us to further understand the characteristics of seismic activity and analyze the regional seismic hazard.In this paper,taking the northeastern Tibetan Plateau as a case study,we establish a three-dimensional visco-elastoplastic finite-element model to simulate earthquake cycles and the spatiotemporal evolution of earthquakes on the model fault system and obtain a seismic catalog on a time scale of tens of thousands of years.On the basis that the model satisfies the regional geodynamics of the northeastern Tibetan Plateau,we analyze seismicity on the northeastern Tibetan Plateau using the simulated synthetic earthquake catalog.The characteristics of earthquake recurrence at different locations and different magnitudes,and the long-term average probability of earthquake occurrence within the fault system on the northeastern Tibetan plateau are studied.The results are a reference for regional seismic hazard assessment and provide a basis for the physics-based numerical prediction of earthquakes.展开更多
The assessment of seismicity is strongly dependent on the recorded events as data base. A uniform catalog of earthquakes in Iran and neighbouring regions is provided to use for seismic hazard assessment of the countr...The assessment of seismicity is strongly dependent on the recorded events as data base. A uniform catalog of earthquakes in Iran and neighbouring regions is provided to use for seismic hazard assessment of the country. Since the recurrence time of maximum credible earthquake can not be estimated directly from m b, empirical relationships for different seismotectonic provinces are established to convert m b to M S , which is a suitable magnitude scale for our purpose. It emerges from completeness study of the catalog that many small and moderate earthquakes are missed out, specially in the historical and early instrumental time periods.展开更多
Taiwan is a region with very high seismicity where hundreds of earthquakes with ms occurred per year and more than 40 with m≥7 since 1900 due to it is located at the boundary of collision between Eurasian and the Phi...Taiwan is a region with very high seismicity where hundreds of earthquakes with ms occurred per year and more than 40 with m≥7 since 1900 due to it is located at the boundary of collision between Eurasian and the Philippine Sea plates.The magnitudes for the same event from these two catalogs of Taiwan and Beijing are different due to diferent data sources selected and different magnitude scales used. To measure sizes of Taiwan events in uniform magnitude scale, the author adopted a catalog of earthquakes with uniform local magnitude scale (Shin, 1993)compiled by Cheng (1996) in compiling a new catalog of Chinese earthquakes. To measure sizes of Taiwan events,we adopted uniform local magnitude scale for events with 5≤M<6. For event with M≥6 we still adopted IASPEI surface wave magnitude scale. Thus the statistic difference between two magnitude values from Taiwan and Beijing in magnitude interval 5≤M<6 reflects difference between Taiwan uniform local magnitode scale and Beijing surface wave magnitude scale. The statistic difference in magnitude interval he6 reflects difference between IASPEI surface wave magnitude scale and Beijing surface wave magnitude scale. Three data sources from "Wang","Cheng" and "Chinese mainland" of Taiwan events with m≥7 are given in this paper, in order to obtain a complete catalog.The statistic result indicates that Taiwan magnitude is slightly larger than Beijing magnitude for 998 events with 5≤M<6. The mean difference is about 0.13 of magnitude unit with deviation 0.32. Similarly, the mean difference is about 0.09 of magnitude unit with deviation 0.23 for 298 eventS with m≥6. We also noted that the difference of magnitude values between Beijing and Taiwan surface wave magnitUdes changed in different time period.Before 1971, most Taiwan magnitude values of the events is larger than Beijing’s. In contrast, most Beijing magnitude values of the events are larger than Taiwan magnitUde values aller 1972. It is probably related to data sources. Three catalogs of events with m≥7 are given in this paper Wang’s catalog (1995) includes 44 events with M≥7, Cheng’s (1996) 39 events and Chinese catalog, before 1911 compiled by Min (1995), 1912-1990 compiled by Wang, et al (1997) and 1991-1998 compiled by Yang, includes 41 events. The variety of these data sources discussed in this paper can be a useful reference for seismologists who use catalog seismic data do their research.However the statistic results and empirical relations presented in this paper can not be used for converting between magnitude scales, since some of them are not the original observation values. In addition, three catalogs of events with M≥ 7 given in this paper can be used for seismicity research comprehensively.展开更多
Geostatistics belongs to the wide class of statistical methods. It is used and applied to analyze and predict the values associated with spatial or spatio-temporal phenomena such as seismological events. Thus, in addi...Geostatistics belongs to the wide class of statistical methods. It is used and applied to analyze and predict the values associated with spatial or spatio-temporal phenomena such as seismological events. Thus, in addition to its adaptability to perform spatial data analysis based on the principles of variography, many other methods more representative of the spatial distributions of the epicentres have been experimented. The unidirectional or isotropic fractal variogram associates the criterion of variance with the fractal dimension which is a better descriptive parameter of the spatial organization of events. The same analysis procedure carried out through a directional or azimuthal variogram introduces the context of a preferential direction of earthquake evolution. Moreover, b-value is a privileged seismological parameter that can be studied alone or in combination with other more advanced geostatistical analysis factors such as fractals, fractal dimensions and the anisotropic variogram. All these concepts were used as methodology for a protocol of analysis of the catalog of the Algeria seismicity including 1919 events for the period extending from 1673 to 2010. This catalog is provided by the compilation of partial catalogs synthesized by the CRAAG (Research Centre in Astronomy, Astrophysics and Geophysics).展开更多
利用Apache+PHP+php My Admin+My SQL5.0的方式建设环渤海虚拟台网地震数据管理平台,实现对地震事件、震相信息、台站参数的管理,同时增加地震矢量分布图等功能,管理员通过程序后台管理实现用户分级、上传下载修改信息记录,保证系统使...利用Apache+PHP+php My Admin+My SQL5.0的方式建设环渤海虚拟台网地震数据管理平台,实现对地震事件、震相信息、台站参数的管理,同时增加地震矢量分布图等功能,管理员通过程序后台管理实现用户分级、上传下载修改信息记录,保证系统使用安全。该系统投入使用后提高了滨海虚拟台网数据的利用率,实现滨海虚拟台网与天津台网的区域统一编目功能,解决了区域台网无法使用国家地震统一编目系统的问题,保证了地震观测质量。展开更多
基金supported jointly by National Key R&D Program of China(No.2018YFC1503400)National Natural Science Foundation of China projects(Nos.41774067,U2039204,and 42074046)+2 种基金Science for Earthquake Resilience(No.XH20082Y)US National Science Foundation(No.1941719)University of California at Riverside.
文摘We present a high-resolution seismic catalog for the 2021 M_(S)6.4/M_(W)6.1 Yangbi sequence.The catalog has a time range of 2021-05-01 to 2021-05-28,and contains~8,000 well located events.It captures the features of the whole foreshock sequence and the early aftershocks.We designed a detection strategy incorporating both an artificial intelligent(AI)picker and a matched filter algorithm.Here,we adopt a hybrid AI method incorporating convolutional and recurrent neural network(CNN&RNN)for event detection and phase picking respectively(i.e.CERP),a light-weight AI picker that can be trained with small volume of data.CERP is first trained with detections from a STA/LTA and Kurtosis-based method called PAL,and then construct a rather complete template set of~4,000 events.Finally,the matched filter algorithm MESS augments the initial detections and measures differential travel times with cross-correlation,which finally results in precise relocation.This process gives 9,026 detections,among which 7,943 events can be well relocated.The catalog shows as expected power-law distribution of frequency magnitude and reveals detailed pattern of seismicity evolution.The main features are:(1)the foreshock sequence images simple fault geometry with consistent strike,but also show a variable event depth along strike;(2)the mainshock ruptures the same fault of the foreshock sequence and activate conjugate faults further to the southeast;(3)complex seismicity are developed in the post-seismic period,indicating complex triggering mechanisms.Thus,our catalog provides a reliable basis for further investigations,such as b-value studies,rupture process,and triggering relations.
文摘West Africa is considered a region of low seismicity. However, the monitoring of earthquake activity by local seismic arrays began very early (as early as 1914) in West Africa but seismic catalogs are very incomplete. In 1991, Bertil studied the seismicity of West Africa based on networks of seismic stations in Ivory Coast and neighboring countries. The reference work of Ambraseys and Adams as well as the recent earthquakes given by the international data centres on the seismicity of West Africa were also used for the computations of earthquake hazard parameters. Different earthquake event data have been compiled and homogenised to moment magnitude (</span><i><span style="font-family:Verdana;">M</span><sub><span style="font-family:Verdana;">w</span></sub></i><span style="font-family:Verdana;">). The obtained catalog covers a period of over four centuries (1615-2021) and contains large historical events and recent complete observations. The complete catalog part has been subdivided into four complete subcatalogs with each a level of completeness. The minimum magnitude and the maximum observed magnitude are equal to 2.89 and 6.8 respectively for the whole catalog. The seismic code software developed by Kijko was used to calculate the earthquake hazard parameters. The results give a </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">b</span></i></span></span><span><span><span> </span></span></span><span><span><span><span style="font-family:Verdana;">value of 0.83 ± 0.08 for the whole period and preliminary seismic hazards curves are also plotted for re</span><span style="font-family:Verdana;">turn periods 25, 50 and 100 years. This is a good and practical example</span><span style="font-family:Verdana;"> showing that this procedure can be used for seismic hazard assessment in West Africa.
基金supported by China Earthquake Science Experiment Project,CEA(Grant No.2019CSES0112)National Natural Science Foundation of China(Grant Nos.41574085,41974107,41590865&U1839207)。
文摘The analysis of seismic hazards relies on the statistical analysis of historical seismic data and the instrumental seismic catalog to obtain the regional earthquake recurrence interval and earthquake probability.The accuracy of analysis thus depends strongly on the completeness of the seismic data used.However,available seismic catalogs are too short or incomplete for the reliable analysis of the statistical characteristics of earthquakes.If a long-term synthetic seismic catalog can be generated using a physics-based numerical simulation,and the simulation results match the crustal deformation,seismicity,and other observations,then such a synthetic catalog helps us to further understand the characteristics of seismic activity and analyze the regional seismic hazard.In this paper,taking the northeastern Tibetan Plateau as a case study,we establish a three-dimensional visco-elastoplastic finite-element model to simulate earthquake cycles and the spatiotemporal evolution of earthquakes on the model fault system and obtain a seismic catalog on a time scale of tens of thousands of years.On the basis that the model satisfies the regional geodynamics of the northeastern Tibetan Plateau,we analyze seismicity on the northeastern Tibetan Plateau using the simulated synthetic earthquake catalog.The characteristics of earthquake recurrence at different locations and different magnitudes,and the long-term average probability of earthquake occurrence within the fault system on the northeastern Tibetan plateau are studied.The results are a reference for regional seismic hazard assessment and provide a basis for the physics-based numerical prediction of earthquakes.
文摘The assessment of seismicity is strongly dependent on the recorded events as data base. A uniform catalog of earthquakes in Iran and neighbouring regions is provided to use for seismic hazard assessment of the country. Since the recurrence time of maximum credible earthquake can not be estimated directly from m b, empirical relationships for different seismotectonic provinces are established to convert m b to M S , which is a suitable magnitude scale for our purpose. It emerges from completeness study of the catalog that many small and moderate earthquakes are missed out, specially in the historical and early instrumental time periods.
文摘Taiwan is a region with very high seismicity where hundreds of earthquakes with ms occurred per year and more than 40 with m≥7 since 1900 due to it is located at the boundary of collision between Eurasian and the Philippine Sea plates.The magnitudes for the same event from these two catalogs of Taiwan and Beijing are different due to diferent data sources selected and different magnitude scales used. To measure sizes of Taiwan events in uniform magnitude scale, the author adopted a catalog of earthquakes with uniform local magnitude scale (Shin, 1993)compiled by Cheng (1996) in compiling a new catalog of Chinese earthquakes. To measure sizes of Taiwan events,we adopted uniform local magnitude scale for events with 5≤M<6. For event with M≥6 we still adopted IASPEI surface wave magnitude scale. Thus the statistic difference between two magnitude values from Taiwan and Beijing in magnitude interval 5≤M<6 reflects difference between Taiwan uniform local magnitode scale and Beijing surface wave magnitude scale. The statistic difference in magnitude interval he6 reflects difference between IASPEI surface wave magnitude scale and Beijing surface wave magnitude scale. Three data sources from "Wang","Cheng" and "Chinese mainland" of Taiwan events with m≥7 are given in this paper, in order to obtain a complete catalog.The statistic result indicates that Taiwan magnitude is slightly larger than Beijing magnitude for 998 events with 5≤M<6. The mean difference is about 0.13 of magnitude unit with deviation 0.32. Similarly, the mean difference is about 0.09 of magnitude unit with deviation 0.23 for 298 eventS with m≥6. We also noted that the difference of magnitude values between Beijing and Taiwan surface wave magnitUdes changed in different time period.Before 1971, most Taiwan magnitude values of the events is larger than Beijing’s. In contrast, most Beijing magnitude values of the events are larger than Taiwan magnitUde values aller 1972. It is probably related to data sources. Three catalogs of events with m≥7 are given in this paper Wang’s catalog (1995) includes 44 events with M≥7, Cheng’s (1996) 39 events and Chinese catalog, before 1911 compiled by Min (1995), 1912-1990 compiled by Wang, et al (1997) and 1991-1998 compiled by Yang, includes 41 events. The variety of these data sources discussed in this paper can be a useful reference for seismologists who use catalog seismic data do their research.However the statistic results and empirical relations presented in this paper can not be used for converting between magnitude scales, since some of them are not the original observation values. In addition, three catalogs of events with M≥ 7 given in this paper can be used for seismicity research comprehensively.
文摘Geostatistics belongs to the wide class of statistical methods. It is used and applied to analyze and predict the values associated with spatial or spatio-temporal phenomena such as seismological events. Thus, in addition to its adaptability to perform spatial data analysis based on the principles of variography, many other methods more representative of the spatial distributions of the epicentres have been experimented. The unidirectional or isotropic fractal variogram associates the criterion of variance with the fractal dimension which is a better descriptive parameter of the spatial organization of events. The same analysis procedure carried out through a directional or azimuthal variogram introduces the context of a preferential direction of earthquake evolution. Moreover, b-value is a privileged seismological parameter that can be studied alone or in combination with other more advanced geostatistical analysis factors such as fractals, fractal dimensions and the anisotropic variogram. All these concepts were used as methodology for a protocol of analysis of the catalog of the Algeria seismicity including 1919 events for the period extending from 1673 to 2010. This catalog is provided by the compilation of partial catalogs synthesized by the CRAAG (Research Centre in Astronomy, Astrophysics and Geophysics).
文摘利用Apache+PHP+php My Admin+My SQL5.0的方式建设环渤海虚拟台网地震数据管理平台,实现对地震事件、震相信息、台站参数的管理,同时增加地震矢量分布图等功能,管理员通过程序后台管理实现用户分级、上传下载修改信息记录,保证系统使用安全。该系统投入使用后提高了滨海虚拟台网数据的利用率,实现滨海虚拟台网与天津台网的区域统一编目功能,解决了区域台网无法使用国家地震统一编目系统的问题,保证了地震观测质量。
