2017年九寨沟发生的Ms7。0级地震未形成明显的地震地表破裂，但引发的次生地质灾害尤为严重，主震南北部呈现明显的破坏性差异，其中北部受灾较南部严重。该文基于Cut and Paste方法，对九寨沟地震余震序列北段中3级以上地震开展震源机制参数反演，并针对其中2次Ms4。1地震使用震源时频特征法进行了破裂方向性测定，结果显示此次九寨沟地震可能触发了岷江断裂带分支断层的活动，结合震源机制及余震分布推测该分支断层为具有一定逆冲性质的右旋走滑断层。综合地震灾害特征、地质构造和余震分布揭示了该分支断层的激活是九寨沟地震北段滑坡等地质灾害多发、地表破坏程度较重的主要原因。
The Characteristics of Earthquake Sequence and Seismic Disaster Effects of the Jiuzhaigou Earthquake on August 8,2017
Although the 2017 Jiuzhaigou Ms7.0 earthquake did not result in significant surface ruptures,the secondary geological disasters it triggered were particularly severe,with the northern area of mainshock suffering more severely than the southern area.Source parameter inversion for earthquakes(M≥3)in the northern segment of the Jiuzhaigou earthquake sequence is conducted based on the Cut and Paste method.Rupture directivities of two Ms4.1 earthquakes are determined by using the source time-frequency characteristic method.Besults show that the Jiuzhaigou earthquake may have triggered the activity of a branch fault within the Minjiang fault zone.Based on the source mechanisms and distribution of the aftershocks,we speculate that this fault is a right-lateral strike-slip fault with a certain thrust component.Furthermore,the structural characteristics of the geological faults,the distribu-tion of aftershocks,and the directivity of seismic ruptures provide a satisfactory explanation for the mechanism un-derlying the triggering of numerous secondary disasters in the northern segment of the Jiuzhaigou earthquake.
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