摘要
2021年M7.4玛多地震是发生在青藏高原巴颜喀拉块体内部的一次左旋走滑型地震,地表沿发震断层——江错断裂形成了150 km长的破裂带和分叉现象.本研究基于玛多地震主震及余震的三维空间分布特征,依据断层走向与倾角的分段变化构建了江错断层的三维精细模型,并顾及GNSS速度场、采用黏弹性本构关系、依据库仑破裂准则,利用ANSYS有限元计算并分析了江错断层面上的应力演化过程.结果表明:江错断层面西段末端浅部区域(<10 km)、中段深部区域(>10 km)以及东段末端区域的库仑破裂应力积累速率和等效应力要显著大于其他区域,与玛多地震主震及余震序列存在较好的空间对应关系,意味着高水平的应力积累是诱发玛多主震及余震发育的主要原因.同时,地表沿江错断层分布的高应力区与玛多地震地表破裂带位置基本一致,表明玛多地震对地表高应力区产生的扰动是导致地表破裂的原因.而在震源深度(17 km)水平面内,江错断层东段末端应力集中区的空间范围远大于该处已发余震的分布范围,暗示玛多地震序列并不会使得江错断裂东段积累的构造应力全部释放;结合模拟揭示的江错断裂断层面上应力扩展趋势,推测巴颜喀拉块体东南区域可能是未来发震的高风险区.
2021 Madoi earthquake(M=7.4), a left-lateral strike-slip earthquake happened in Bayan Har block which lies on the Tibetan plateau, caused obvious surface ruptures with length of 150 km along the seismogenic Jiangcuo fault and of branching pattern at both ends of rupture zones. In this study, based on the segmental features of fault inclinations and strikes obtained from the three-dimensional(3 D) spatial distribution of epicenters of mainshock and its aftershocks, a 3 D finite element model of seismogenic fault was constructed, and the evolution of tectonic stress on the seismogenic fault was investigated numerically by considering the GNSS velocity field, viscoelastic constitutive relation, and the Coulomb criterion. The results illustrate that the accumulative velocities of Coulomb stress and the effective tectonic stress at three regions, including the ends of west(<10 km) and east sections of the seismogenic fault, and the region corresponding to the hypocenter of mainshock, are significantly larger than that at other places on the fault, which are spatially consistent with the Madoi earthquake series. Therefore, the tectonic stresses in high values are expected to be the main factor leading to the earthquakes. In addition, the stresses distributed on ground surface show high values along the Jiangcuo fault and spatially relate to the locations of surface ruptures, which indicates that the surface ruptures are mainly caused by the ground stress disturbances due to the mainshock and its aftershocks. Moreover, in terms of the tectonic stress distribution at the depth of hypocenter, the size of stress concentration region at the east section of the seismogenic fault is overwhelmingly larger than the area of aftershocks occupying, which implies that the Madoi earthquake might have only released part of the accumulated stress at the east section of the seismogenic fault. On basis of the trends of tectonic stress evolutions, we suggest that the southern east part of the Bayan Har block might be a potential seismic
作者
吴立新
卢菁琛
毛文飞
胡俊
周子龙
李志伟
齐源
姚汝冰
WU LiXin;LU JingChen;MAO WenFei;HU Jun;ZHOU ZiLong;LI ZhiWei;QI Yuan;YAO RuBing(School of Geoscience and Info-Physics,Central South University,Changsha 410083,China;Laboratory of Geohazard Perception,Cognition and Prediction,Central South University,Changsha 410083,China;School of Resource and Safety Engineering,Central South University,Changsha 410083,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第10期3844-3857,共14页
Chinese Journal of Geophysics
基金
国家自然基金项目(41930108,42101394,42030112)
国家重点研发项目(2018YFC15035)资助。
关键词
玛多地震
构造应力演化
有限元模拟
库仑破裂应力
地表破裂
Madoi earthquake
Tectonic stress evolution
Finite element method(FEM)simulation
Coulomb failure stress
Ground surface ruptures
