The seismicity in the middle section of the Altyn Tagh Fault System Revealed by a Dense Nodal Seismic Array

Abstract

The left-lateral Altyn Tagh Fault (ATF) system is the northern boundary of the Tibetan Plateau, separating the Tarim Basin and the Qaidam Basin. The middle section of ATF has not recorded any large earthquakes, so the potential seismic hazard is unclear. We developed an earthquake catalog using continuous waveform data recorded by the Tarim-Altyn-Qaidam dense nodal seismic array from 17 September to 23 November 2021 in the middle section of ATF. With the machine learning-based picker, phase association, location, match and locate workflow, we detected 233 earthquakes with ML -1-3, far more than 6 earthquakes in the routine catalog. Combining with focal mechanism solutions and the local fault structure, we find that seismic events are clustered along the ATF with strike-slip focal mechanisms and on the southern secondary faults with thrusting focal mechanisms. This overall seismic activity in the middle section of the ATF might be due to the northeastward transpressional motion of the Tibetan Plateau block at the western margin of the Qaidam Basin.