珊溪水库M_L4.6震群精确定位与发震构造研究

Precise Relocation and Seismogenic Structure of the Shanxi Reservoir Earthquake Sequence in Wenzhou,Zhejiang Province

利用浙江、福建区域地震台网和珊溪水库台网给出的P波走时资料,通过震源位置和速度结构联合反演方法,重新确定了珊溪水库地震的震源参数。并通过假设发震断层可以用一个平面进行拟合的思路,利用重新确定的震源参数拟合得到了发震断层面参数。收集了2267条P波到时数据,求解了ML4.0以上地震震源机制解,结合水库区的断层活动性特征和宏观调查资料,讨论了珊溪水库地震序列的发震构造。

Using P-wave＇s travel time recorded by Shanxi-Reservoir Seismological Network,Zhejiang Seismological Network,and Fujian Seismological Network,we implemented a simultaneous inversion of the earthquake relocation and velocity structure,and got the new location of the ML4.6 earthquake in Shanxi-Reservoir area.Assuming the seismogenic fault can be fitted with a plane,we fitted the fault parameters with the new source parameters of the shanxi-resevoir earthuqake.We collected P-wave＇s first-motion data of 313 earthquakes to calculate the focal-mechanism solutions of the ML4.0 earthuqakes.Refering to the characteristics of fault zones crossing the reservoir and the data of the seismic macro-survey of the reservior area,we discussed the seismogenic structure of the Shanxi Reservoir area.We find that：① The focal depth of the earthquake sequence in Shanxi-Reservoir area is at an average of 5.4 km,smaller than the one in South China.② Beside the reservoir the focus is shallower,but deeper in the reservoir inundation area.In the beginning of the reservoir-induced seismicity,the focal depth increased gradually,because the deep infiltration of water gradually induced an earthquake with a greater depth.③ By fitting the epicenters of Shanxi earthquake sequence,we got the earthquake fault plane parameters：fault strike 132°,dip 85°,tend direction southwest.The fault parameters were broadly consistent with the ones of the Shuangxi-Jiaoxiyang fault.The ML≥4.0 focal mechanism solutions of the nodal plane,strike,dip,P-axis azimuth and elevation were generally in good agreement.