2022年1月8日青海门源M6.9地震余震精确定位与断层面拟合

Relocation and fault plane fitting of the Menyuan M6.9 earthquake on January 8, 2022

摘要:

利用青海和周边87个地震台站于2022年1月8—13日记录的青海门源M6.9地震主震及680次余震资料,经双差地震定位重新进行震源位置的修定,获得633个地震重新定位后的震源信息。结果显示,此次地震的余震分布明显以昌马—俄博断裂南末梢端为界分为东、西两段,西段呈近EW向沿托勒山断裂东段分布,东段呈NWW向沿冷龙岭断裂西段分布。重新定位前余震初始震源深度集中分布在5~15 km,重新定位后变化为在0~20 km深度范围内偏正态分布。根据重新定位后余震分布特点并参考地表破裂带的展布,依据成丛地震发生在断层附近的原则,选取2个矩形区域,基于这2个区域内重新定位后的震源信息,利用模拟退火与高斯\|牛顿相结合的算法进行断层面拟合计算,完整地获得每一个拟合区域的断层面参数。结果表明托勒山断裂东段断层面与冷龙岭断裂西段断层面分别为长约15 km总体走向为近EW向的高倾角左旋走滑断裂与长约12 km总体走向为NWW向的高倾角大型左旋走滑断裂。此次青海门源地震可能是上述两断层面末端相互挤压共同破裂形成的。

Abstract:

Based on the data of the Menyuan M6.9 earthquake and 680 aftershocks recorded by 87 seismic stations in Qinghai Province and its adjacent areas from January 8 to 13, 2022, the earthquakes were relocated by the double-difference location method, and the source parameters for 633 earthquakes were obtained. Results show that the distribution of aftershocks is divided into east and west sections, with the southern tip of the Changma-Ebo fault as the boundary. The west section is distributed along the eastern segment of the Tuoleshan fault in a nearly EW direction, and the east section is distributed along the western section of the Lenglongling fault in an NWW direction. The focal depths of aftershocks concentrate at 5-15 km before relocation, while those after relocation are normally distributed in a depth range of 0-20 km. According to the distribution characteristics of aftershocks after relocation and the distribution of the surface rupture zone, two rectangular areas were selected on the basis of the principle that cluster earthquakes occur near the fault. Based on the relocated focal information in the two areas, the fault plane fitting calculation was conducted using the simulated annealing and Gauss-Newton algorithms and the fault plane parameters of each fitting area were obtained. Results show the following: the fault plane in the eastern segment of the Tuoleshan fault is a high-dip left-lateral strike-slip fault with nearly EW direction and a length of approximately 15 km; the fault plane in the western segment of the Lenglongling fault is a high-dip left-lateral strike-slip fault with NWW direction and a length of approximately 12 km. This earthquake may be caused by the mutual extrusion and rupture of the ends of the two aforementioned fault planes.