2022年门源MS6.9地震震区三维速度与发震机制研究

Three-dimensional velocity structure and seismogenic mechanism of Menyuan MS6.9 earthquake in 2022

摘要:

2022年1月8日，青海省门源县发生M_S6.9地震。使用青海、甘肃等区域数字台网所观测到的2009年1月1日—2022年2月8日间青海门源及周边地区(36°～39°N，101°～104°E)14 869次地震事件的地震观测资料，基于双差成像(TomoDD)方法进行重定位分析，结果表明：门源及周边地区地震震源深度较浅，主要集中在5～15 km深度范围，其中10 km附近分布最多。推断该深度区域为门源及周边地区的主要孕震区。基于地震重定位结果和主震区三维速度结构分别对2016年门源M_S6.4地震和此次地震序列的发震机理进行分析对比，发现两次地震都位于高速异常体边缘，速度结构与断裂、地震序列吻合较好。2022年门源地震位于高速体的西端末梢位置，是该高速体受青藏高原东北缘顺时针应力作用导致的滑动产生的走滑型地震。

Abstract:

On January 8, 2022, an M_S6.9 earthquake occurred in Menyuan County, Qinghai Province. In this paper, the seismic data of 14 869 events in Menyuan and its surrounding areas (36°-39°N, 101°-104°E) observed by regional digital stations in Qinghai and Gansu from January 1, 2009 to February 8, 2022 were relocated by using the double difference tomography (Tomodd) method. The results showed that the focal depth of earthquakes in Menyuan and its surrounding areas are mainly concentrated in a depth range of 5-15 km, especially at near 10-km depth. It is inferred that this depth area is the main seismogenic area in the study area. Based on the seismic relocation results and the three-dimensional velocity structure of the mainshock area, the seismogenic mechanisms of the 2016 Menyuan M_S6.4 earthquake and the 2022 Menyuan M_S6.9 earthquake were analyzed and compared. It is found that two earthquakes are both located at the edge of high-velocity anomaly block, and the velocity structure corresponds well to local fault and two earthquake sequences. The 2022 Menyuan M_S6.9 earthquake, located at the western tip of the high-velocity body, is a strike-slip earthquake caused by the sliding of the high-velocity body due to the clockwise stress on the northeast edge of the Qinghai-Tibet Plateau.