Using the data of regional seismic network, this paper analyzes the current faulting behaviors of different segments of the Anninghe-Zemuhe fault zone, western Sichuan, and identifies the likely risky segments for pot...Using the data of regional seismic network, this paper analyzes the current faulting behaviors of different segments of the Anninghe-Zemuhe fault zone, western Sichuan, and identifies the likely risky segments for potential large earthquakes. The authors map the probable asperities from the abnormally low b-value distribution, develop and employ a method for identifying current faulting behaviors of individual fault segment from the combinations of multiple seismicity parameter values, and make an effort to estimate the average recurrence intervals of character-istic earthquakes by using the parameters of magnitude-frequency relationship of the asperity segment. The result suggests that the studied fault zone contains 5 segments of different current faulting behaviors. Among them, the Mianning-Xichang segment of the Anninghe fault has been locked under high stress, its central part is probably an asperity with a relatively large scale. The Xichang-Puge segment of the Zemuhe fault displays very low seismicity under low stress. Both the locked segment and the low-seismicity segment can be outlined on the across-profile of relocated hypocenter depths. The Mianning-Xichang segment is identified to be the one with potential large earth-quake risk, for which the average recurrence interval between the latest M = 6.7 earthquake in 1952 and the next characteristic event is estimated to be 55 to 67 years, and the magnitude of the potential earthquake between 7.0 and 7.5. Also, it has been preliminarily suggested that for a certain fault segment, its faulting behaviors may change and evolve with time gradually.展开更多
本文基于地面测量布格异常和EIGEN-6C4(European Improved Gravity model of the Earth by New techniques version 6C4)重力资料,以USTClitho2.0(Unified Seismic Tomography models for continental China lithosphere version 2.0)...本文基于地面测量布格异常和EIGEN-6C4(European Improved Gravity model of the Earth by New techniques version 6C4)重力资料,以USTClitho2.0(Unified Seismic Tomography models for continental China lithosphere version 2.0)岩石圈结构模型为约束,利用顾及地壳密度横向变化的布格改正、小波多尺度分解、均衡改正、Moho面重力反演和岩石圈有效弹性厚度(T_(e))反演等方法,计算了郯庐断裂带中南段布格异常及其多尺度分解结果、深部均衡异常、Moho面深度、岩石圈有效弹性厚度及荷载比,结合地震活动性和地球物理资料,综合分析了该地区重力异常构造背景及其与地震活动性的关系.结果表明,沿郯庐断裂带的重力异常在嘉山以南段、嘉山-新沂段和新沂-安丘段呈显著差异性3段式分布,且与地震活动性分段特征高度统一.地震活动性强的嘉山以南段和新沂-安丘段具有浅部布格异常线性条带、深部布格异常高梯度带、Moho面陡变带或上隆带、地壳重力不均衡、低岩石圈有效弹性厚度和高荷载比特征,表明其深部结构破坏程度高,岩石圈力学强度低,且存在均衡调整作用,有利于应力及时释放,因而地震活动频繁;地震活动性弱的嘉山-新沂段浅部布格异常散乱,深部布格异常高值区和低值正均衡异常区穿过郯庐断裂带,Moho面变化平缓,岩石圈有效弹性厚度值高,荷载比低,对应扬子地块俯冲于华北断块区之下的遗留深部构造,其深部结构破坏程度较低,岩石圈力学强度大,且均衡调整作用不强,岩石圈不易发生破裂,因而地震频率很低.郯城8.5级地震位于横穿郯庐断裂带的深部构造北缘附近,是最易于积累应力的部位,深部构造和岩石圈有效弹性厚度剧烈变化导致应力分布不均匀以及较强的均衡调整作用可能是地震的触发因素.嘉山-新沂段具备有利于应力长期积累的深部构造条件,应持续关注其应力积累状态和强震风险.展开更多
Tibet has often been called the “Roof of the World”. The plateau is probably the largest and highest area ever to exist in Earth history, with an average elevation exceeding 5000m. The uplifting of the Tibetan Plate...Tibet has often been called the “Roof of the World”. The plateau is probably the largest and highest area ever to exist in Earth history, with an average elevation exceeding 5000m. The uplifting of the Tibetan Plateau is the result of continent\|continent collision. This process is still going on and is significant for us to understand the formation and the evolution of global continent.It’s generally accepted is act as the northern boundary of the Tibetan Plateau is the Altyn Tagh Fault. The Altyn Tagh Fault is recognized as a large\|scale left\|lateral strike\|slip fault, many studies indicate it is the northern margin of the eastward extruded of crustal blocks and the northern boundary of the Plateau as well. Compared to the knowledge on the southern plateau and the Himalaya, we know much less about the northern plateau and the Altyn Tagh Fault. Some people have already begun to realize the importance of the latter for the revealing the uplifting of the Plateau.展开更多
基金Chinese Joint Seismological Science Foundation (102002).
文摘Using the data of regional seismic network, this paper analyzes the current faulting behaviors of different segments of the Anninghe-Zemuhe fault zone, western Sichuan, and identifies the likely risky segments for potential large earthquakes. The authors map the probable asperities from the abnormally low b-value distribution, develop and employ a method for identifying current faulting behaviors of individual fault segment from the combinations of multiple seismicity parameter values, and make an effort to estimate the average recurrence intervals of character-istic earthquakes by using the parameters of magnitude-frequency relationship of the asperity segment. The result suggests that the studied fault zone contains 5 segments of different current faulting behaviors. Among them, the Mianning-Xichang segment of the Anninghe fault has been locked under high stress, its central part is probably an asperity with a relatively large scale. The Xichang-Puge segment of the Zemuhe fault displays very low seismicity under low stress. Both the locked segment and the low-seismicity segment can be outlined on the across-profile of relocated hypocenter depths. The Mianning-Xichang segment is identified to be the one with potential large earth-quake risk, for which the average recurrence interval between the latest M = 6.7 earthquake in 1952 and the next characteristic event is estimated to be 55 to 67 years, and the magnitude of the potential earthquake between 7.0 and 7.5. Also, it has been preliminarily suggested that for a certain fault segment, its faulting behaviors may change and evolve with time gradually.
文摘本文基于地面测量布格异常和EIGEN-6C4(European Improved Gravity model of the Earth by New techniques version 6C4)重力资料,以USTClitho2.0(Unified Seismic Tomography models for continental China lithosphere version 2.0)岩石圈结构模型为约束,利用顾及地壳密度横向变化的布格改正、小波多尺度分解、均衡改正、Moho面重力反演和岩石圈有效弹性厚度(T_(e))反演等方法,计算了郯庐断裂带中南段布格异常及其多尺度分解结果、深部均衡异常、Moho面深度、岩石圈有效弹性厚度及荷载比,结合地震活动性和地球物理资料,综合分析了该地区重力异常构造背景及其与地震活动性的关系.结果表明,沿郯庐断裂带的重力异常在嘉山以南段、嘉山-新沂段和新沂-安丘段呈显著差异性3段式分布,且与地震活动性分段特征高度统一.地震活动性强的嘉山以南段和新沂-安丘段具有浅部布格异常线性条带、深部布格异常高梯度带、Moho面陡变带或上隆带、地壳重力不均衡、低岩石圈有效弹性厚度和高荷载比特征,表明其深部结构破坏程度高,岩石圈力学强度低,且存在均衡调整作用,有利于应力及时释放,因而地震活动频繁;地震活动性弱的嘉山-新沂段浅部布格异常散乱,深部布格异常高值区和低值正均衡异常区穿过郯庐断裂带,Moho面变化平缓,岩石圈有效弹性厚度值高,荷载比低,对应扬子地块俯冲于华北断块区之下的遗留深部构造,其深部结构破坏程度较低,岩石圈力学强度大,且均衡调整作用不强,岩石圈不易发生破裂,因而地震频率很低.郯城8.5级地震位于横穿郯庐断裂带的深部构造北缘附近,是最易于积累应力的部位,深部构造和岩石圈有效弹性厚度剧烈变化导致应力分布不均匀以及较强的均衡调整作用可能是地震的触发因素.嘉山-新沂段具备有利于应力长期积累的深部构造条件,应持续关注其应力积累状态和强震风险.
文摘Tibet has often been called the “Roof of the World”. The plateau is probably the largest and highest area ever to exist in Earth history, with an average elevation exceeding 5000m. The uplifting of the Tibetan Plateau is the result of continent\|continent collision. This process is still going on and is significant for us to understand the formation and the evolution of global continent.It’s generally accepted is act as the northern boundary of the Tibetan Plateau is the Altyn Tagh Fault. The Altyn Tagh Fault is recognized as a large\|scale left\|lateral strike\|slip fault, many studies indicate it is the northern margin of the eastward extruded of crustal blocks and the northern boundary of the Plateau as well. Compared to the knowledge on the southern plateau and the Himalaya, we know much less about the northern plateau and the Altyn Tagh Fault. Some people have already begun to realize the importance of the latter for the revealing the uplifting of the Plateau.
