珊溪水库地震小震震源机制解特征研究

利用P波初动和直达P、S波最大速度振幅比联合求解小震震源机制的方法求出珊溪水库ML2.0以上地震的震源机制,得到了珊溪水库震源机制各参数时空特征如下:主压应力为SN向,主张应力为EW向,应力主要为水平应力,发震断层倾角较大且多为走滑断层。在个别4级左右地震前P轴方位都有偏离再恢复的现象。在北纬27.65°～27.69°间,P轴方位集中在0°±30°或者180°±30°,节面走向集中在45°±15°或者135°±15°。震源深度大于4km的地震倾角多集中在70°～90°度之间。

Study on the Characteristic of Focal Mechanism Solutions of the Shanxi Reservoir Earthquake

Using P wave first motions and the maximum velocity amplitude ratio of Pg and Sg waves,the focal mechanism solutions of the Shanxi reservoir earthquakes above ML 2.0were calculated.The time and space characteristics of the focal mechanism solutions parameters were obtained as follow:most of the main press stresses are North-south oriented,most of the main tensile stresses are East-west oriented,the stresses are almost horizontal,most of the slips of the planes are above 60°,and most of the faults are strike-slip type.Both of the azimuths of the Paxis have the trend of first deviation and then recovery before some MS4.0earthquakes.In the range from 27.66°to 27.69°N,focal mechanism solutions parameters have a good consistency.Most of the azimuths of the P-axis are 0±30°and 180±30°,and most of strikes of the plane are 45±15°and 135±15°.Most of the slips with focal depths deeper than 4km are between 70°and 90°.