中文摘要：

采用CAP（Cut and Paste）方法反演了2015年11月23日青海祁连MS5.2主震的震源机制解,其最佳双力偶解：节面Ⅰ走向109°、倾角58°、滑动角21°,节面Ⅱ走向8°、倾角72°、滑动角146°,矩震级MW5.16,矩心震源深度约为9km。结合震区的活动构造,判定发震断层面为节面Ⅰ,推测托勒山北缘活动断裂中段为此次地震的发震断裂。

英文摘要：

On November 23, 2015, an Ms5.2 earthquake occurred at Qilian county, Qinghai province. By the end of the first day of December, 48 aftershocks had occurred in the mainshock seismic region, including 34 ML1.0~1.9 aftershocks, ten ML2.0~2.9 aftershocks, and four ML3.0~3.9 aftershocks, with the greatest magnitude being ML3.4. In this paper, based on the seismic network data of Gansu and Qinghai provinces, we use the cut-and-paste method to calcu- late the focal mechanism solution of the Qilian Ms5.2. We then use the waveform fitting method for synthetic and observed seismograms to further determine the focal depth of the earthquake. The results indicate that this event occurred on a rupture plane （strike 109°, dip 58°, and slip 21°） , which demonstrated a left-lateral strike-slip mechanism with a minor reverse-faulting com- ponent, a moment magnitude of Mw5.16, and a centroid depth of about 9 km. The other nodal plane was characterized by a strike of 8°, dip of 72°, and a slip of 146°. The focal mechanism,which describes the nature and source of the rupture process, provides an important foundation for understanding the stress state of the source region and the earthquake faults, and for analy- zing the causes of a seismic event. A comparison of the maps of focal mechanism solutions for the Qilian MsS.2 earthquake and historical earthquakes illustrates that the focal mechanism of this earthquake is in keeping with historical focal mechanisms. Therefore, based on our comprehen- sive analysis, we can identify the middle of the north Tuoleshan active fault as the seismogenic structure of this event.