Coupling fraction and relocking process of the Longmenshan Fault Zone following the 2008 Mw7.9 Wenchuan earthquake

Abstract The analysis of post-seismic fault relocking and healing is crucial for predicting future seismic risk in seismogenic regions. In this study, we investigated the dynamic characteristics of the coupling fraction and relocking process of the Longmenshan Fault Zone (LFZ) following the 2008 Mw7.9 Wenchuan earthquake. Analysis was performed using Global Positioning System (GPS) velocity data for the periods 2009–2011, 2011–2013, 2013–2015, and 2015–2018, combined with cross-fault levelling data from 2008 to 2017. The results show that following short-term creep caused by the Wenchuan earthquake, the northeastern section of the LFZ rapidly began relocking process, and that today, the fault plane is close to being fully coupled; following the subsequent 2013 Mw6.6 Lushan earthquake, coupling fraction along part of the middle section of the LFZ, southwest of the Wenchuan earthquake source, gradually increased, which are basically consistent with fault healing results indicated by permeability and seismic wave velocity. The Wenchuan earthquake also accelerated strain accumulation rates and enhanced coupling along the southwestern section of the LFZ. Following the Lushan earthquake, only local areas of the southwestern section were decoupled, limiting the release of accumulated strain energy. The aftershock gap between the Wenchuan and Lushan earthquakes, and the aftershock gap southwest of the Lushan earthquake remain strongly coupled and continue to accumulate strain energy; as such, seismic risk remains high in these two segments.