Abstract: The Pishan M_S6.5 earthquake occurred in the west Kunlun piedmont area. According to the surface deformation data obtained by the Pishan M_S6.5 earthquake emergency field investigation team, combined with the positioning accuracy of spatial distribution of aftershocks information, the focal mechanism solutions and deep oil profile data, we think the Pishan M_S6.5 earthquake is a typical thrust faulting event, and the seismogenic structure is the Pishan reverse fault-anticline, which did not produced obvious surface fault zone on the surface. In the vicinity of the core of the Pishan anticline, we found some tensional ground fissures whose strikes are all basically consistent with the anticline. We propose that the surface deformation is caused by the folding and uplift of the anticline. The Pishan earthquake is a typical folding earthquake. The tectonic deformation of the west Kunlun piedmont is dominated by the thickening and shortening of the upper crust which is the typical thin-skinned nappe tectonic. The Pishan earthquake occurred in the frontal tectonic belt, the root fault of the nappe structure has not been broken, and we should pay attention to the seismic risk of the Tekilik Fault.

Key words: Pishan M_S6.5, west Kunlun, bending moment fault, fold earthquake

摘要： 皮山M_S6.5地震发生在西昆仑山前的皮山逆断裂-褶皱带上，该构造带的变形特征以地层的褶皱弯曲为主，在背斜顶部发育的一系列正断层是背斜顶部局部拉张应力产生的弯矩断层。根据皮山地震应急科考资料，结合精定位后的余震空间分布信息、震源机制解和深部石油剖面等资料认为，皮山M_S6.5地震是1次逆冲型破裂事件。本次地震在地表没有产生明显的地震断层，但在背斜顶部形成多条与背斜走向一致的地裂缝；这些裂缝是地震致使背斜隆升褶皱，在背斜地层转折部位弯曲褶皱幅度最大的地带产生的构造裂缝，是背斜活动的直接反映；本次地震属于1次典型的褶皱地震。西昆仑山前的构造变形以上地壳地层的缩短和增厚为主，地震孕育模型属于典型的薄皮推覆构造，本次地震发生在推覆体前缘的皮山背斜上，推覆体根部断裂尚未发生破裂，其未来的地震危险性值得进一步关注和研究。

关键词: 皮山M_S6.5地震, 西昆仑, 弯矩断层, 褶皱地震