Recently in 2020, in southern Saudi Arabia three felt earthquakes occurred in Asir region, in the Khamis Mushait, Ahad Rafidah, and AL-Shuqiq area, of magnitude 3.45, 3.1, and 3.5, respectively. The most interesting e...Recently in 2020, in southern Saudi Arabia three felt earthquakes occurred in Asir region, in the Khamis Mushait, Ahad Rafidah, and AL-Shuqiq area, of magnitude 3.45, 3.1, and 3.5, respectively. The most interesting event was the earthquake that occurred in Khamis Mushait area, along a lake formed behind the Tadhah Dam (~7 km), fearing any damage to the dam’s body and the consequent destruction. Moment tensors for each event were computed for determining fault plane solutions, seismic moment, moment magnitude (Mw) and the CLVD ratio. In addition, the frequency contents in the waveforms of each event were identified. The obtained focal mechanisms represent different styles of faulting, normal movement with strike slip and strike slip with reverse. These tectonic movements on faults parallel to the Red Sea refer to the tensional forces due to the Red Sea rift system. These events occurred due to a natural tectonic movement, with considering the Khamis Mushait event as an induced event because of the lake behind the Dam. Many previous seismic hazard assessment studies have been conducted in southern Saudi Arabia without considering these recent seismic sources. Thus, our study provides new information related to detecting of new active seismic sources, which contributes to updating studies of seismic risk assessment in this region. In addition, our study pushes us to establish other additional seismic stations around these new seismic sources. This in turn will play a pivotal role in controlling seismic sources and then reassessing the seismic hazard in southern Saudi Arabia.展开更多
Purpose: When producing mining operations in high-stress rock massive, technogenic seismicity is manifested. Forecasting and prevention of these events is given much attention in all countries with a developed mining ...Purpose: When producing mining operations in high-stress rock massive, technogenic seismicity is manifested. Forecasting and prevention of these events is given much attention in all countries with a developed mining industry. From the point of view of the paradigm of physical mesomechanics, which includes a synergetic approach to changing the state of rock massive of different material composition, this problem can be solved with the help of monitoring methods tuned to the study of hierarchical structural media. Changes in the environment, leading to short-term precursors of dynamic phenomena, are explained within the framework of hierarchical heterogeneity and nonlinearity from observations of wave fields and seismic catalog. For that purpose it is needed to develop new algorithms of modeling wave field propagation through the local objects with hierarchical structure. Design/Methodology/Approach: It had been constructed an algorithm for 3D modeling electromagnetic field for arbitrary type of source of excitation in N-layered medium with a hierarchic conductive and magnetic intrusion, located in the layer number J. It had been constructed algorithms for 2D modeling of sound diffraction and linear polarized transversal seismic wave on an anomaly elastic or dense intrusion of hierarchic structure, located in the layer number J of N-layered elastic medium. We used the method of integral and integral-differential equations for a space frequency presentation of wave field distribution. Findings: From the theory it is obvious that for such complicated medium each wave field contains its own information about the inner structure of the hierarchical inclusion. Therefore it is needed to interpret the monitoring data for each wave field apart, and not mixes the data base. Practical Value/Implications: These results will be the base for constructing new systems of monitoring observations of dynamical geological systems. Especially it is needed to prevent rock shocks in deep mines by their exploitation or natural hazards.展开更多
Based on the seismic source model in the Fifth Generation Seismic Ground Motion Parameters Zonation Map of China(FGSGMPZMC),a new seismic fault model,the new zonation of seismic risk areas(SRAs),and the estimation of ...Based on the seismic source model in the Fifth Generation Seismic Ground Motion Parameters Zonation Map of China(FGSGMPZMC),a new seismic fault model,the new zonation of seismic risk areas(SRAs),and the estimation of seismicity rates for 2021-2030,this study constructed a new time-dependent seismic source model of China’s mainland,and used the probabilistic seismic hazard analysis method to calculate seismic hazard by selecting the ground motion models(GMMs)suitable for seismic sources in China.It also provided the probabilities of China’s mainland being affected by earthquakes of modified Mercalli intensity(MMI)Ⅵ,Ⅶ,Ⅷ,Ⅸ,and≥Ⅹin 2021-2030.The spatial pattern of seismic hazards presented in this article is similar to the pattern of the FGSGMPZMC,but shows more details.The seismic hazards in this study are higher than those in the FGSGMPZMC in the SRAs and fault zones that can produce large earthquakes.This indicates that the seismic source model construction in this study is scientific and reasonable.There are certain similarities between the results in this study and those of Rong et al.(2020)and Feng et al.(2020),but also disparities for specific sites due to differences in seismic source models,seismicity parameters,and GMMs.The results of seismic hazard may serve as parameter input for future seismic risk assessments.The hazard results can also be used as a basis for the formulation of earthquake prevention and mitigation policies for China’s mainland.展开更多
文摘Recently in 2020, in southern Saudi Arabia three felt earthquakes occurred in Asir region, in the Khamis Mushait, Ahad Rafidah, and AL-Shuqiq area, of magnitude 3.45, 3.1, and 3.5, respectively. The most interesting event was the earthquake that occurred in Khamis Mushait area, along a lake formed behind the Tadhah Dam (~7 km), fearing any damage to the dam’s body and the consequent destruction. Moment tensors for each event were computed for determining fault plane solutions, seismic moment, moment magnitude (Mw) and the CLVD ratio. In addition, the frequency contents in the waveforms of each event were identified. The obtained focal mechanisms represent different styles of faulting, normal movement with strike slip and strike slip with reverse. These tectonic movements on faults parallel to the Red Sea refer to the tensional forces due to the Red Sea rift system. These events occurred due to a natural tectonic movement, with considering the Khamis Mushait event as an induced event because of the lake behind the Dam. Many previous seismic hazard assessment studies have been conducted in southern Saudi Arabia without considering these recent seismic sources. Thus, our study provides new information related to detecting of new active seismic sources, which contributes to updating studies of seismic risk assessment in this region. In addition, our study pushes us to establish other additional seismic stations around these new seismic sources. This in turn will play a pivotal role in controlling seismic sources and then reassessing the seismic hazard in southern Saudi Arabia.
文摘Purpose: When producing mining operations in high-stress rock massive, technogenic seismicity is manifested. Forecasting and prevention of these events is given much attention in all countries with a developed mining industry. From the point of view of the paradigm of physical mesomechanics, which includes a synergetic approach to changing the state of rock massive of different material composition, this problem can be solved with the help of monitoring methods tuned to the study of hierarchical structural media. Changes in the environment, leading to short-term precursors of dynamic phenomena, are explained within the framework of hierarchical heterogeneity and nonlinearity from observations of wave fields and seismic catalog. For that purpose it is needed to develop new algorithms of modeling wave field propagation through the local objects with hierarchical structure. Design/Methodology/Approach: It had been constructed an algorithm for 3D modeling electromagnetic field for arbitrary type of source of excitation in N-layered medium with a hierarchic conductive and magnetic intrusion, located in the layer number J. It had been constructed algorithms for 2D modeling of sound diffraction and linear polarized transversal seismic wave on an anomaly elastic or dense intrusion of hierarchic structure, located in the layer number J of N-layered elastic medium. We used the method of integral and integral-differential equations for a space frequency presentation of wave field distribution. Findings: From the theory it is obvious that for such complicated medium each wave field contains its own information about the inner structure of the hierarchical inclusion. Therefore it is needed to interpret the monitoring data for each wave field apart, and not mixes the data base. Practical Value/Implications: These results will be the base for constructing new systems of monitoring observations of dynamical geological systems. Especially it is needed to prevent rock shocks in deep mines by their exploitation or natural hazards.
基金sponsored by the Special Fund of the Institute of Geophysics,China Earthquake Administration(Grant Nos.DQJB22Z03 and DQJB22B25)。
文摘Based on the seismic source model in the Fifth Generation Seismic Ground Motion Parameters Zonation Map of China(FGSGMPZMC),a new seismic fault model,the new zonation of seismic risk areas(SRAs),and the estimation of seismicity rates for 2021-2030,this study constructed a new time-dependent seismic source model of China’s mainland,and used the probabilistic seismic hazard analysis method to calculate seismic hazard by selecting the ground motion models(GMMs)suitable for seismic sources in China.It also provided the probabilities of China’s mainland being affected by earthquakes of modified Mercalli intensity(MMI)Ⅵ,Ⅶ,Ⅷ,Ⅸ,and≥Ⅹin 2021-2030.The spatial pattern of seismic hazards presented in this article is similar to the pattern of the FGSGMPZMC,but shows more details.The seismic hazards in this study are higher than those in the FGSGMPZMC in the SRAs and fault zones that can produce large earthquakes.This indicates that the seismic source model construction in this study is scientific and reasonable.There are certain similarities between the results in this study and those of Rong et al.(2020)and Feng et al.(2020),but also disparities for specific sites due to differences in seismic source models,seismicity parameters,and GMMs.The results of seismic hazard may serve as parameter input for future seismic risk assessments.The hazard results can also be used as a basis for the formulation of earthquake prevention and mitigation policies for China’s mainland.
