Spatiotemporal variation of gravity field and inter-seismic correlation analysis of the 2021 Maduo and 2022 Menyuan earthquakes

The spatiotemporal evolution of the gravity field is a comprehensive response to deep crustal material migration and tectonic deformation processes, and contains key precursory information for the seismogenic stage of earthquakes. Based on mobile gravity observation data collected in the northeastern Tibetan Plateau from 2015 to 2021, this study obtained multi-spatiotemporal-scale gravity field changes before and after the earthquakes through classical adjustment. In light of the regional tectonic framework and deep dynamic background, we systematically analyzed, from a gravity perspective, the relationship between the spatiotemporal dynamic gravity changes and the preparation and occurrence of the 2021 Maduo M S 7.4 earthquake and the 2022 Menyuan M S 6.9 earthquake, and explored the possible association between the two earthquakes. The main findings are as follows: (1) The significant gravity changes observed before the 2021 Maduo M S 7.4 earthquake and the 2022 Menyuan M S 6.9 earthquake are closely related to regional tectonic activity, and these changes may have mainly originated from deep crustal material adjustment and migration processes. (2) The pattern of gravity changes in the northeastern Tibetan Plateau has a clear spatial correspondence with the locations of strong earthquakes. Both the Maduo and Menyuan earthquakes occurred near the turning points of gravity high-gradient zones and around the centers of the four-quadrant pattern. (3) The gravity changes in the Menyuan seismic region were significantly enhanced following the Maduo earthquake, We inferred that the Maduo earthquake may have caused some perturbation to the tectonic stress state in the Menyuan region, indirectly influencing the occurrence of the subsequent Menyuan earthquake. (4) The gravity change maps show that the gravity anomaly areas and gravity gradient zones before the Maduo and Menyuan earthquakes are highly correlated, possibly implying a close relationship between the two events in terms of deep-seated tectonic processes.