Abstract: In this research,we made a primary research on the Coulomb stress triggering of the March 11,2011 M_W=9.0 Tohoku earthquake sequence by using the software of Coulomb 3.2,the earthquake rupture models obtained by Hayes and Guangfu Shao et al. , and the aftershocks data from Harvard CMT catalogue(Centroid Moment Tensor)and Japan F-net catalogue. Our results suggest that: Firstly,the M_W7.2 foreshock,which occurred on March 9,has stress triggering effect on the M_W9.0 main shock; Secondly,the statistical result of the aftershocks triggered by the main shock shows that different statistical results would be obtained when using different main shock rupture model,aftershock catalogue,equivalent friction coefficient and different nodal plane of focal mechanism as the receive plane. The minimum and maximum triggering rates of main shock to aftershock are 56.8%and 75.3%,respectively; and thirdly,when calculating the Coulomb stress by using earthquake focal mechanism,the shear stress on the two nodal planes is the same theoretically. However,in actual calculation,the shear stress would be different between the two nodal planes,due to the non-orthogonality of the two nodal planes or rounding off decimal places in the focal mechanism results. But,the difference of the shear stress on the two nodal planes is relatively small. More attention should be paid on the selection of receiver fault plane from the two nodal planes,when discussing the stress triggering of one specific earthquake or making statistics of aftershock triggering rate,because the selection of receiver fault plane would have a certain effect on the shear stress,and have greater effect on the normal stress,thus the Coulomb stress would be affected.

Key words: stress triggering, M_W9.0 Japan earthquake, fault plane, foreshock, aftershock

摘要： 选用Hayes和Guangfu Shao等给出的震源破裂模型(2011年3月网上公布)、哈佛CMT目录和日本F-net目录给出的余震目录,使用Coulomb3.2软件,对2011年3月11日发生在日本本州东海岸附近海域的M_W9.0地震序列间的静态库仑应力触发关系进行了初步研究。结果表明: 1)3月9日发生的M_W7.2前震破裂分布产生的库仑应力对随后发生的M_W9.0主震存在触发作用; 2)M_W9.0主震对余震的触发统计结果表明,选用不同的主震模型、余震目录、等效摩擦系数和震源机制解中不同的节面作为接收断层面时,会得到不同的触发统计结果,该研究得到的主震对余震的触发率最小为56.8%,最大为75.3%; 3)利用震源机制解计算库仑应力时,理论上震源机制解的2个节面上的剪切应力是相同的,但在实际计算中可能由于2个节面的非正交或震源机制解结果的取整,导致2个节面上计算出的剪切应力不同,但一般差异很小。由于节面的选取对接收断层面上的剪切应力有一定影响,而对接收断层面上正应力的影响较大,因而会影响到库仑应力的计算结果,因此讨论某个具体余震是否被触发或统计余震触发率时,对接收断层面的选取应加以注意。

关键词: 应力触发, 日本9.0级地震, 断层面, 前震, 余震