新疆伽师强震区余震序列的地震台阵定位

RELOCATION OF EARTHQUAKE SEQUENCES USING JOINT HYPOCENTER DETERMINATION METHOD: PORTABLE SEISMIC ARRAY STUDY IN JIASHI REGION, XINJIANG

1998年中国地震局地质研究所在伽师强震群区布设了 30台流动宽频带地震台 ,记录到比纳木及龙口两个强震 (M≥ 6 0 )的主震及余震序列。我们利用Geiger法和JHD方法对这两个地震序列进行了台阵定位。结果表明 :1)利用地震台阵数据的JHD定位结果可以较好地确定地震序列的相对空间位置 ,并且比Geiger法有更高的精度 ;2 )比纳木、龙口地震序列勾画出了两条不平行的SWW向断层 ,其走向及产状与相应主震的矩张量研究结果基本吻合 ,此地震序列可作为确定伽师强震群震源断层面的重要参考依据 ;3)比纳木和龙口地震序列发生在壳幔界面的梯度带上及壳内高、低速介质交界部位 ,这表明地震的形成与地壳深部构造环境密切相关 ;4 )伽师强震群具有张性破裂特征 。

In 1997, 7 strong earthquakes ( M >6.0) occurred in Jiashi region, Xinjiang Uygur Autonomous Region. In order to gain an insight into this seldom seen seismic event, a passive broadband seismic array experiment was carried out by the Institute of Geology, China seismological Bureau in 1998. During the experiment two events, the Binamu and Lonkou earthquakes ( M ≥6.0), and their aftershock sequences were recorded by the portable seismic array. In this paper, these two earthquake sequences are relocated by using the Geiger method and the Joint Hypocenter Determination (JHD) method, respectively. The results show that: 1) the JHD method can be used to locate the relative position of an aftershock sequence more precisely than the Geiger method; 2) the Binamu and Longkou aftershock sequences delineate two nonparallel SWW trending faults, the occurrence of which are roughly consistent with those given by the moment tensor solution of the corresponding main shocks, and hence can be used for determining the focal plane of the Jiashi events; 3) the Binamu and Longkou earthquakes occurred at the gradient zone of the crust mantle boundary and at the convergence of the crustal high and low velocity media nearby the deep faults; this may indicate that the genesis of these earthquakes bears a close relation to the deep geological environment within the crust; 4) the tensional rupturing feature of the Jiashi earthquake sequence might be resulted from the heterogeneous lateral deformation of the northern edge of the Tarim basin.