关中陕南地区一些小地震震源参数和环境剪应力的研究

Source parameters and ambient Stress of small earthquakes in Shaannan And Guanzhong Region

对2001年9月～2002年6月间发生在关中陕南地区42次小地震,利用数字地震记录资料,进行了波谱分析和震源参数的测定,并分析了环境剪应力分布特征。结果显示关中陕南地区环境剪应力处于较低水平,应力值3.3×105～32.2×105Pa之间,西部12×105～32×105Pa略高于东部8×105～17×105Pa,中部最低。西部有两个应力值较高区,一个是宝鸡、眉县、凤翔附近区域较高值区,应力值20×105～32×105Pa,另一个是留坝、凤县附近区域较高值区,应力值20×105～37×105Pa之间。东部的较高值区是高陵、耀县、三原附近地区,应力值在16×105～18×105Pa之间,该区域曾发生1998年1月5日泾阳MS4.8级地震。

focal parameters of the small earthquakes occurred in Guanzhong and Shaannan region from Sep.2001 to Jun. 2002 are determined with digital records, and the source spectra as well as the character of ambient stress distribution are analyzed. The result show that the ambient shear stress is lower in Guanzhong and Shaannan region, between 3.3×105～32.2×105Pa, but the western part (12×105～32×105Pa) is higher than the eastern part(8×105～17×105Pa), the central part is lowest. There are two higher region in west part, one is Baoji, Meixian, Fengxiang and its surrounding region, 20×105～32×105Pa, another is Liuba, Fengxian and its surrounding region, 20×105～37×105Pa. The higher region in eastern part is Gaoling, Yaoxian, Sanyuan and its surrounding region, 16×105～18×105Pa. An MS4.8 earthquake occurred in Jingyang of the region on Jan 5, 1998.