内蒙古中西部地区小震震源机制解分析

FOCAL MECHANISM ANALYSIS OF SMALL EARTHQUAKE IN CENTRAL AND WESTERN INNER MONGOLIA

利用P、S最大振幅比数据反演中小震震源机制方法,选取2001—2008年发生在内蒙古中西部的中小地震的数字波形数据,反演得到130个地震震源机制。研究结果表明,震源机制存在NWW-SEE向和NE-SW向的两组节面,受近NEE-SWW方位的压应力和NNW-SSE方位的张应力作用,NWW-SEE向的破裂面产生右旋走向滑动,NNW-SSE向的破裂面产生左旋走向滑动。系统聚类分析显示,内蒙古中西部中小地震以直立节面、走滑型震源机制解为主。通过对杭锦旗、托克托两次4级以上地震震源机制与背景场对比,认为均不是"前兆地震"。通过对震源机制的一致性参数分析,内蒙古中西部震源机制一致性参数出现低值区,对地震预测具有一定的指示意义。

Using the method of the maximum amplitude ratio between P and S to inverse the focal mechanisms of small and medium earthquakes, and by using the digital waveform data of the small and medium earthquake occurred in the central and western Inner Mongolia from 2001 to 2008, 130 focal mechanisms were obtained. The resuits show that there are two groups of nodal plane in NWW-SEE and NE-SW. From the effect of the compressive stress in NEE-SWW direction and the tensile stress in NNW-SSE direction, the NWW-SEE break side results in the right sliding, the NNW-SSE one in the left sliding. Systemic clustering analysis shows that small and medium earthquakes in the central and western Inner Mongolia were mostly with the section of vertical surface and strike-slip focal mechanism solution. By contrasting the focal mechanism of Hangjinqi and Tuoketuo Ms4 earthquakes with the background field, it is found that both of them are not precursor earthquakes. Through the analysis of consistency focal mechanism of parameters, there is a low value area of focal mechanism parameters in the central and western Inner Mongolia, it may have a certain significance to earthquake prediction.