2001年昆仑山口西MS8.1地震破裂时空过程的统一模型

An Unified Model of Spatiotemporal Rupture Process for the 2001 West of Kunlun Mountain Pass Earthquake

摘要:

2001年昆仑山口西M_S8.1地震经历了一个复杂的破裂过程，其破裂长、幅度大、破裂速度多变，成为大陆型地震研究的典型地震。本文融合近场高精度大地测量观测（4幅InSAR影像，34个GPS点位同震位移）和高信噪比远震波形记录，基于有限断层反演理论，联合反演得到该地震同震破裂时空过程的统一模型；同时，基于欧洲区域台网波形数据，利用反投影方法获得高频破裂的时空展布。联合反演结果表明，破裂自西向东传播的过程中走向有所变化，破裂尺度达400km，最大滑移量达8m，地震矩大小为6.1×10²⁰Nm，对应的矩震级M_W为7.78。主断层破裂经历了3个阶段，其中，超剪切破裂阶段对应最大位错区域，破裂到达西大滩段与昆仑山口断层交叉处时，破裂速度与尺度迅速下降。反投影结果同样显示破裂的3个阶段空间上对应大地测量反演的3个最大破裂区，最大破裂区的扩展速度达6km/s，但超剪切破裂终止在断层交叉口东部约30km处断层走向发生转变的位置。

Abstract:

The Kunlun Mountain Pass earthquake in 2001 experienced a complicated rupture process with long rupture length, large amplitude and variable velocity, which has become a model case of continental earthquake study. Based on the near-field high-resolution geodetic data(4 InSAR image, 34 GPS points coseismic displacement) and high signal to noise ratio teleseismic waveform, the unified model of the coseismic rupture process is obtained by joint inversion based on finite fault theory. At the same time, the waveform data of the regional network in Europe are collected, and the time and space distribution of the high-frequency rupture is obtained by back projection method. The joint inversion results show that the rupture scale is 400km, the seismic moment is 6.1×10²⁰Nm, and the corresponding moment magnitude is 7.78. The main fault rupture has experienced three stages, the supershear rupture stage corresponds to the largest dislocation area, and the rupture velocity and scale decrease rapidly when it breaks to the intersection between the Xidatan section and the Kunlun Mountain Pass fault. The back projection result shows three stages of rupture, which correspond to the three largest rupture zones of geodetic inversion in space, and the propagation speed of the largest rupture zone reaches 6km/s, but the super-shear rupture stops at the position where the fault strike changes about 30km east of the fault intersection.