伽师地震区地壳细结构及发震断层的初步研究  

A PRELIMINARY STUDY ON FINE STRUCTURES OFJIASHI EARTHQUAKE REGION AND EARTHQUAKEGENERATING FAULT

作　　者：李松林[1] 张先康[1] W.D.Mooney 赖晓玲[1] A.J.Michael 段永红[1] 

机构地区：[1]中国地震局地球物理勘探中心,郑州450002 [2]美国地质调查局,美国ca94025

出　　处：《地球物理学报》2002年第1期76-82,T001,T002,共9页Chinese Journal of Geophysics

基　　金：国家重点基础研究发展规划 ( 973)项目 ( 95 -1 3-0 2 -0 2 );地震科学联合基金重点课题 ( 95 -0 7-4 1 4 )联合资助

摘　　要：1997年至 1 998年伽师地区共出现 9次震级为 6 .1— 6 .8级的强震 .在一个非常短的时间间隔内和非常小的地区范围内接连出现这么多次震级非常接近的地震 ,确实非常罕见 .为研究伽师强震区的深部构造背景和孕震机制 ,本文对伽师地震区的余震观测资料进行了分析处理 .利用联合反演技术同时得到了地震震源位置和地震区地壳三维速度结构 .余震震中沿一北北东向条带分布 ,与强震分布的两个条带中的北东向条带位置基本重合 .三维反演得到的速度结构结果表明 ,在地下 1 2km以下存在一条北北东向和一条北北西向的低速条带 .上述两低速条带与强震分布的两个条带位置很接近 .初步推测 ,低速条带对应了地壳深部的两条断裂 .在我们观测期间 ,北北东向断裂有微震活动 ,北北西向断裂相对平静 .It is very unusual that nine large earthquakes of similar magnitudes (M=6.1_6.8) occurred within a very small area and a very short period of time (1997_1998) in Jiashi of Xinjiang Province, Northwest China. This paper analyzes the observed data of the aftershocks in the Jiashi earthquake region for studying the generating mechanism and deep structural background of the Jiashi strong earthquake swarm. The simultaneous inversion method was used to calculate the hypocenter positions and 3-D velocity structure of this region. The results show that the aftershocks concentrated in a NNE-trending belt, which roughly coincides with the NE-trending belt of the two strong earthquake belts. Velocity structure obtained from 3-D inversion suggests that there exist two low velocity zones, one trending NNE and the other NNW, below the depth of 12 km. These low velocity zones are almost consistent with the two strong earthquake belts. The preliminary results lead to the conclusion that the low velocity zones correspond to two deep crustal faults. At the time of our observation, microearthquakes took place on the NNE-trending fault, while the NNW-trending fault was relatively quiescent.

关 键 词：伽师地震群 速度结构 断层成像 联合反演 地质构造 地壳 

分 类 号：P315.2[天文地球—地震学]