1976年唐山7．8级地震震区现今地震震源机制分析

Focal Mechanism Analysis of the Recent Earthquakes in Tangshan Seismic Region of M7.6 in 1976

利用首都圈数字地震台网记录,采用双差定位法对1976年唐山地震震区近年来发生的中小地震重新定位,获得1998个高精度结果,据此将震区划分为中、东、西3个分布特征不同的区。唐山7.8级主震所在的中区南部地震分布走向NNE,主震震中北部转为NE向;滦县7.1级余震所在的东区地震分布呈"丁"字形;宁河6.9级余震所在的西区地震分布没有明显优势方向。反演得到198个地震的震源机制解,对进一步划分的5个子区分别给出平均解的应力轴取向,并结合震源位置讨论了唐山地震序列的震源构造。

Based on the records recorded by Digital Seismic Network in Capital Area, 1998 accurate relocating results for the mid-small earthquake occurred in Tangshan seismic region in 1976 are obtained with Double-Difference Method. According to the characteristics, the seismic region can be divided into 3 sub-regions. The southern part of middle region with NNE strike, where the M7.8 main shock located, and turns to NE strike in the northern part. The eastern part shows a T shape where the Luanxian M7.1 earthquake located. There is no preponderant strike in the western part, where the M6. 9 earthquake located. 198 focal mechanisms are obtained by inversion, and the direction of mean stress axis is given respectively for the 5 divided sub regions. The focal structure of Tangshan earthquake series is discussed with hypocenter locations.