1927年古浪8级大震区小震重新定位及问题讨论

联合利用甘肃及周边测震台网记录的古浪及周边地区4 592次地震的P波绝对到时和相对到时资料,采用双差地震定位方法对古浪震源区小震进行重新定位后发现,皇城-双塔断裂带东、西两段表现出不同的力学运动性质,西段以逆冲运动为主,地震主要发生在断裂的下盘;而东段地震却主要发生在上盘,断层活动以局部拉张为主。还首次发现在皇城-双塔断裂带的中段与主破裂呈垂直方向存在一条主震发生时新产生的共轭断层,基于小震的断层面参数反演显示该断裂是一高倾角运动性质以右旋为主兼具正断的断裂。

Discussion of Small Earthquake Relocation in the Area of the 1927 Gulang M8 Earthquake

Based on the data recorded by 67 stations in the Gansu digital seismic network and its adjacent seismic network from 2000 to 2015, we relocated 4 592 small earthquakes that occurred at the epicenter of the 1927 Gulang M8 earthquake and in its adjacent areas via a double-difference earthquake relocation algorithm. The results show that the eastern and western segments of the Huangcheng-Shuangta fault zone exhibit different mechanical motion properties. While the western segment is primarily dominated by thrust faulting, and earthquakes occurred mainly in the footwall of the fault, and in the eastern segment earthquakes mainly occurred in the hanging wall of the fault. Moreover, we first found a conjugate fault located in the middle segment of the Huangcheng-Shuangta fault that nearly perpendicular to the main fault. Based on the inversion of fault parameters of these small earthquakes, we also found that this high dip-angle fault mainly exhibits right-lateral strike-slip faulting with a minor tension component.