Abstract: Based on the rupture models of the 2015 Pishan M_W6.4 earthquake and half space homogeneous elastic model, the Coulomb stress changes generated by the earthquake are calculated on the active faults near the earthquake region. The horizontal stress changes and the displacement field are estimated on the area around the epicenter. Results show that:(1)The Coulomb stress is decreased in the west of the western Kunlun frontal thrust fault(9.5×10³Pa), and increased in the east of the western Kunlun frontal thrust fault and the middle of the Kangxiwa faults. More attention should be taken to the seismic rick of the east of the western Kunlun frontal thrust fault; (2)Based on the analysis on the location of the aftershocks, it is found that most of the aftershocks are triggered by the earthquake. In the region of increased Coulomb attraction, the aftershock distribution is more intensive, and in the area of the Coulomb stress reduction, the distribution of aftershocks is relatively sparse; (3)The horizontal area stress increases in the north and south of the earthquake(most part of the Qaidam Basin and the northwest of the Qinghai-Tibet plateau), and decreases in the east and west of the earthquake(northern part of the Qinghai-Tibet plateau and eastern part of the Pamir Mountains). In the epicenter area, the principal compressive stress presents nearly NS direction and the principal extensional stress presents nearly EW direction. The principal compressive stress shows an outward radiation pattern centered on the epicenter with the principal extensional stress along the direction of concentric circles. The principal compressive stress presents NW direction to the west of the epicenter, and NE to the east of the epicenter. With the increase of radius, the stress level gradually decays with 10⁷Pa in the epicenter and hundreds Pa in the Maidan Fault which is in the north of the Qaidam Basin.

Key words: 2015 Pishan earthquake, earthquake rupture model, Coulomb stress, stress triggering

摘要： 基于2015年皮山M_W6.4地震的破裂模型及均匀弹性半空间模型，计算了该地震在周围主要活动断层上产生的库仑应力变化和周围地区的水平应力变化。结果表明：1）皮山地震造成西昆仑山前逆冲断裂西段库仑应力降低（达9.5×10³Pa）；西昆仑山前逆冲断裂东段和康西瓦断裂中段的库仑破裂应力增加，因此要注意西昆仑山前逆冲断裂东段的危险性。2）对余震位置的统计分析认为，大多数余震受到主震的触发作用；主震造成周围地区库仑引力增加的部分，余震的分布比较密集；而主震造成的库仑应力减少的部分，余震的分布就比较稀疏。3）水平面应力在该地震震中北侧的柴达木盆地和南侧的青藏高原西北部增加（拉张），在震中东侧的青藏高原北部和西侧的帕米尔高原东部降低（压缩）。从水平主压和主张应力方向来看，震中区域的主压应力为近SN向，主张应力方向为EW向。主压应力以震中为中心呈向外辐射状，而主张应力近乎于以震中为圆心的同心圆。震中西侧的主压应力为NW向，震中东侧为NE向，应力的大小随着半径增加而逐渐衰减，中心达10⁷Pa，到达柴达布盆地北部的迈丹断裂仅有百Pa的水平。

关键词: 2015年皮山地震, 震源破裂模型, 库仑应力, 水平应力