Vertical deformation before and after the 2022 Menyuan Ms6.9 earthquake and analysis of earthquake precursors

This study analyzed the vertical deformation before and after the 2022 Menyuan Ms6.9 earthquake in Qinghai Province, China, using leveling profiles across faults measured from Minle County in Gansu Province to Menyuan County in Qinghai Province. Our results suggest the following: (1) The amplitude of regional vertical differential motion near the Sunna-Qilian and Lenglongling faults within the Qilian Shan increased before the 2022 Menyuan earthquake. It was accompanied by the emergence of high gradient deformation zones. Deformation at the Tongziba cross-fault leveling site near the Sunan-Qilian fault was considerable. In contrast, deformation at the Daliang cross-fault leveling site near the stepover region (adjacent to the epicenter) between the Lenglongling and Tuolaishan faults was minor. After 2018, vertical deformation at the Tongziba site notably accelerated, while that at the Daliang site was insignificant. (2) After the 2022 Menyuan earthquake, 140–150 mm of subsidence deformation occurred near the Daliang site, while the Tongziba site did not experience significant deformation. (3) Vertical deformation before and after the 2022 Menyuan earthquake conforms with the elastic-rebound theory, and the evolution of pre-earthquake deformation was consistent with the strike-slip fault deformation pattern at different seismogenic stages, i.e., the relative motion near the locked fault in the late seismogenic stage gradually weakened. The characteristics of strain accumulation and release derived from the vertical deformation before and after the Menyuan M_S6.9 earthquake help understand the deformation process of earthquake preparation and earthquake precursors.