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逆冲滑动是汶川地震的初始和主要震源过程,其破裂滑动量随断层深度的分布形态与多数板内逆冲强震不一致.本文用摩压比值来表征断层沿线的局部破裂危险程度,通过数值实验讨论了底部破裂源、近地表倾角和无地表破裂的前期地震等对铲形逆冲断层的破裂危险分布和破裂滑动分布的影响.有限元数值模拟结果显示,在巴颜喀拉块体对龙门山断裂带的高强度挤压下,上陡下缓近地表陡倾角的铲形断层形态使得汶川发震断层近地表对逆冲破裂和滑动有一定的阻碍作用;破裂滑动量集中于发震断层中部的前期逆冲地震是造成汶川MS8.0地震逆冲滑动分布异于板内逆冲强震滑动分布现象的一个可行解释.
The thrust slip is the initial and main source process of Wenchuan earthquake, and the distribution of rupture slip with the depth of fault is not consistent with the majority of intraplate thrusts.In this paper, the degree of partial rupture along the fault is characterized by the ratio of friction and pressure, The effects of bottom rupture source, near-surface dip angle and pre-earthquake without surface rupture on rupture distribution and rupture distribution of spallike thrust are discussed experimentally.The results of finite element numerical simulation show that in Bayan Har block Under the high-intensity extrusion of the Longmenshan fault zone, the scoop-like fault shape steeply and steeply approaching the surface steep angle makes the near-surface rupture of the Wenchuan earthquake impede rupture and sliding to a certain extent. The previous thrust earthquake in the central part of the fault is a feasible explanation for the phenomenon that the thrust distribution of Wenchuan MS8.0 earthquake is different from the sliding distribution of the thrust within the plate.