GPS time series inversion of the healing process of the middle segment of the Longmenshan fault after the 2008 Wenchuan earthquake

The analysis of post-seismic fault healing process is important for deepening our understanding of seismogenic mechanisms, seismic faulting theory, and seismic cycles. In this study, by using time series of continuous GPS stations from 2010.30 to 2013.30 between the Wenchuan earthquake and the Lushan earthquake, the dynamic evolution of fault locking and slip deficit rate in the middle-southern segment of the Longmenshan fault zone were inverted and analyzed by the negative dislocation program of TDEFNODE, and the healing process of the middle segment and the background of major earthquakes of the southwest segment were discussed based on the inversion results. The results show that the locking fraction of the ruptured area around the epicenter of the Wenchuan earthquake gradually increased, which was basically in creeping state in 2010, and then in state of strongly locked in 2013. The locked area also gradually increased from the southwest of the Wenchuan earthquake epicenter to the epicenter, which indicates that this part of the fault has been healing rapidly. Most of the ruptured zone in the northeast of the epicenter is still in creeping state and the fault has not yet begun healing. The fault near and southwest of the epicenter of the Lushan earthquake has been in state of strongly locked, and the slip deficit rate of the completely locked area has been decreasing year by year, probably indicating that the healed region shares part of the compression effect of the Bayan Har block on the Sichuan Basin. The above results indicate that the healing process and activity characteristics of different segments of the Longmenshan ruptured fault are significantly different after earthquake. The southwest segment of the Longmenshan fault zone is in state of strongly locked and the background for a major earthquake has strengthened in the case of rapid accumulation of compressive elastic strain.