1996年3月19日新疆伽师M_s6.9地震的震源机制以及相关问题研究

THE FOCAL MECHANISM SOLUTION FOR MARCH 19,1996 M_s6.9 EARTHQUAKE IN XIN-JIANG, JIA-SHI REGION AND RELATED PROBLEMS

利用最早到达地震台的地幔Rayleigh波包（R1）的波形拟合方法估计了1996年3月19日新疆伽师Ms6．9地震的震源机制，其结果是：地震形成左旋压性逆冲断裂，据震源机制解的P轴（－4．15×10（18）Nm，181°，19°）和各向同性分量推测震源区受到近南北向压应力的作用，且有体积压缩效应．据宽频P波列波形随台站方位角的变化估计，破裂从下方开始向上偏东的方向进行．此次地震可能是印度板块与西伯利亚地块相互挤压的表现，标志着伽师及其邻区，或者说兴都库什弧以北地区进入了一次新的地震活动期．这个活动期可能与缅甸弧以北地区，即中缅边界地区的地震活动期相对应，是较大地球动力过程在不同时空点的表现．用本文方法可对Ms6．4以上地震的震源机制进行快速估计．

The source mechanism for March 19, 1996 earthquake of Ms6.9 in Xin-Jiang Jia-Shi region, is estimated using mantle Rayleigh R1 waveform fliting method. The resultS are: A left-lateral, compressional thrust fault was formed by the earthquake. In view of the P axis (-4. 15 ×10(18)Nm, 181°, 19°) and the isotropic component of the seismic moment tensor, the source area was acted by a compressive stress in N-S direction and there was volumetric compression effect in the area. The rupture estimated by the change of the broad band P waveform with station azimuth angles was from a lower point towards upper and east direction. T'he earthquake may be an expression of the collision and extrusion betWeen indian and Eurasian plates, and possibly marked the beginning of a seismic active period in Jia-Shi and itS vicinity or the northern area of Hindu Kush arc. ms active period may of correspond with the seismic active period that is taking place in the northern area of Myanmar arc, that is the area on the boundary between China and Myanmar, and is an expression of a large earth dynamic process in different temporal and spatial pointS. The mechanism of any earthquake whose magnitude is greater than about Ms6.4 can be estimated in very short bine by the method used in the paper.