2013年肃南-门源交界MS5.1地震重新定位、震源机制及发震构造研究
Relocation of 2013 Sunan-Menyuan MS5.1 Earthquake and Analysis of Focal Mechanisms and Seismogenic Structure

针对2013年9月20日甘肃肃南-青海门源交界发生的MS5.1地震,采用Hypo2000定位方法对地震序列中ML ≥ 1.0的事件进行重新定位。重定位后震源位置的水平和垂直方向平均误差分别为1.87 km和3.64 km,走时残差为0.51 s,余震沿冷龙岭断裂的走向分布,长约20 km,宽约2.5 km;横向剖面显示震源深度集中在3~10 km,纵向剖面显示出一个约30°倾角的破裂面。采用CAP方法得到了MS5.1主震的震源机制解,节面I走向360°,倾角68°,滑动角117°;节面Ⅱ走向126°,倾角为34°,滑动角42°,矩震级MW5.05,最佳震源矩心深度10 km。
On September 20, 2013, an earthquake of MS5.1 occurred in the Sunan-Menyuan boundary region. Using the data recorded by Gansu and Qinghai Digital Seismic Networks, we relocated the ML ≥ 1.0 events in the earthquake sequence using the Hypo2000 location algorithm. After relocation, the vertical and horizontal average errors were found to be 1.87 km and 3.64 km, respectively, and the root mean square residual error of travel time is 0.51 s. The results show that the mainshock occurred at the northern foot of Gangshiga, the main peak of Lenglongling, and the aftershocks are primarily distributed along the Lenglongling fault zone, with a length and width of approximately 20 km and 2.5 km, respectively. The transverse section exhibits focal depth focus in 3~10 km, and longitudinal section shows a fracture plane that dips toward the northeast and the dip angle is approximately 30°. The focal mechanism solution of the mainshock is also determined using the cut and paste(CAP) method. The results show that the best double couple solutions of the event and the other nodal plane are 360°, 68°, and 117° and 126°, 34°, and 42°, respectively, for strike, dip, and rake angles. Further, the moment magnitude is MW5.05, and the best centroid depth is 10 km.