【摘要】 利用西藏地震台网记录到的2017年11月18日西藏米林6.9级地震及其余震序列资料,研究此次地震的发震机制断层。双差定位结果显示,余震沿着主震的NW和SE方向往两侧扩展分布,震源深度主要集中在2～12 km,同时从短轴剖面上地震分布推断,此次米林地震的发震断层倾角约为45°。对M_L3.5以上的余震采用CAP方法进行波形拟合震源机制反演,其结果显示,此次米林地震序列震源错动类型以逆冲和走滑为主,比较符合该区域的构造动力环境。应力场反演结果显示,米林地震序列主压应力轴（S₁轴）方向为NNE-NS向,主张应力轴（S₃轴）方向为SEE-SE向;反映的断层错动方式为逆冲兼走滑类型。地震余震序列展布以及震源机制分布显示断层走向和断层特性与帕隆—旁辛断裂的特征较为吻合,推测米林地震的发震断裂为帕隆—旁辛断裂。更多还原

【Abstract】 In this paper,we used the 2017 Millin M6.9 earthquake and its aftershock sequence recorded by the Tibet network to study nucleation mechanisms of the earthquake.Processed by the double-difference positioning method,the aftershocks are shown along the north-west and south-east sides of the main earthquake,whereas the focal depth is mainly concentrated at the range of 2～12 km.Moreover,the aftershock distribution at the short axis shows that the seismogenic fault dips 45°.For the aftershocks above ML3.5,we used the seiscap software to inverse waveform for studying nucleation mechanism.The results show that the main types of dislocation for the Millin earthquake sequence are thrust and strike-slip deformation,which is consistent with the tectonic background of the region.The inversion results of stress fields show that the direction of main compressive stress axis（S₁ axis） is NNENS,whereas the direction of main tensile stress axis（S3 axis） is SEE-SE,which indicates the seismogenic fault is a thrust fault with a strike-slip component.Based on the distribution of aftershock sequence and focal mechanism of the earthquake,we suggest that the seismogenic fault shows a consistent structure with the Palong-Pangxin fault,which indicates that the fault is associated with the earthquake.更多还原