基于库仑应力改变和地震活动性研究巴颜喀拉块体周缘强震序列的触发关系及其构造意义

自本世纪以来，青藏高原巴颜喀拉块体周缘密集地发生了7次M_W≥6.5强震事件，包括伤亡惨重的2008年汶川M_W7.9地震和2017年九寨沟M_W6.5地震。本文根据这7次强震事件中先前地震对后续地震的库仑应力改变（dCFS）的计算结果，结合基于ETAS模型得到的背景地震活动性的变化结果，研究了强震间的触发关系，以试图解释发生在环巴颜喀拉块体的几次强震的发震机理并探讨其构造意义。结果表明，各个强震的库仑应力变化与其造成的背景地震活动性变化呈正相关，并且在这7次强震中，汶川地震对芦山地震有显著的触发作用，并造成芦山地区背景地震活动性的显著提高。同时汶川地震对九寨沟地震的发生具有一定的延迟作用，造成九寨沟地区背景地震活动性降低。除此之外，其它地震之间均无明显的触发/延迟作用或显著的背景地震活动性变化。这表明该强震序列的孕震机制主要是巴颜喀拉块体东南向持续挤压的构造运动，推断巴颜喀拉块体目前仍处于构造运动活跃期，因此包括巴颜喀拉块体周缘在内的我国西南地区未来的强震危险性值得持续关注。 

Triggering relationship in strong earthquake sequence around the Bayan Har block and its tectonic significance based on Coulomb stress changes and seismicity

Seven major earthquakes of M_W≥6.5 have occurred around the Bayan Har block in the Tibetan Plateau since this century, including the devastated 2008 Wenchuan earthquake and the recent 2017 Jiuzhaigou earthquake. Here we investigate the triggering effects among those major earthquakes by calculating the Coulomb stress changes and analyzing the background seismicity rate changes, and furthermore to understand the tectonic activity of the Bayan Har block. Our results show that, the Coulomb stress changes positively correlate with the background seismicity rate changes. Also, the results show that the Wenchuan earthquake triggered the Lushan earthquake and delayed the Jiuzhaigou earthquake. Besides, there is no significant triggering/delay effect among other major earthquakes. These findings imply that the remarkable earthquake sequence results from the southeastward movement of the Bayan Har block, and the Bayan Har block is still in the highly active seismic period. Furthermore, the seismic hazards of the Bayan Har block and its adjacent faults in the southwestern China should be paid more attention.