Kinematics of the Haiyuan Fault (Northwest China) Prior to the 2022 Menyuan Mw 6.7 Earthquake

Menyuan, China, experienced a Mw 6.7 earthquake on 8 January 2022. This study combines GNSS and InSAR data to analyze how fault activity affects earthquake hazard assessment through fault inversion. A time-dependent version of DEFNODE (TDEFNODE) is developed to calculate fault locking and slip deficit through GNSS data and Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR)-processed Sentinel-1A data. The findings reveal that Haiyuan Fault is strongly locked before the earthquake, with a locking depth of around 30 km and a slip deficit rate between 3.1 mm/yr and 5.6 mm/yr. Meanwhile, the cumulative seismic moments correspond to moment magnitudes ranging from Mw 6.49 to Mw 6.75, which are highly consistent with the actual Menyuan earthquake. This indicates that fault locking and slip deficit provide a reference for quantitatively assessing the characteristics of pre-seismic activity. Although the seismic moments derived from different datasets vary from 6.10 × 1018 to 1.50 × 1019 N·m, the key parameters determined by TDEFNODE inversion are generally consistent with the actual focal mechanisms. Therefore, results show that a comprehensive analysis of fault inversion can provide important insights into the formation process of earthquakes and help assess regional earthquake risk.