Seismogenic Structure of the 2017 Ms 6.6 Jinghe, China, Earthquake Inferred from Seismic Detection and Relocation

On 8 August 2017, an Ms 6.6 earthquake occurred in Xinjiang province, Northwest China. As no visible surface ruptures, coupled with the complex regional fault systems, the seismogenic structure of the earthquake is still unclear. Rich aftershock data can constrain the fault structure to some extent, but only a handful of aftershocks were recorded by the China Earthquake Networks Center (CENC) in this case. To augment the CENC catalog, we first relocated aftershocks and then adopted them as templates to scan the continuous waveforms five days before and five days after the mainshock using the Match and Locate method. We successfully detected 3.5 times more events than the CENC catalog, and the detected events discernibly feature a south-dipping plane. Amalgamating the focal mechanism of the mainshock and available geological information, the south-dipping thrust Jinghenan fault is inferred to be the rupture fault of the Jinghe earthquake. In addition, we find that the detected foreshocks are mainly distributed on the northwest edge of asperity where the mainshock may have nucleated. In addition, based on the cluster analysis and spatial-temporal evolutions of detected events, we speculate that a backthrust branch related to the seismogenic fault was activated during the aftershocks moving significantly westward in the first 30 min after the mainshock occurrence.