Fault locking behavior of the Longmenshan Thrust Belt preceding the 2008 Wenchuan earthquake

Fault locking inversion can clarify the occurrence mechanisms of large earthquakes and the seismic hazards of future earthquakes. Due to limited observations in mainland China, fault locking inversions have typically been unstable. To investigate a more suitable fault locking behavior of the Longmenshan Thrust Belt (LTB) preceding the 2008 Wenchuan earthquake, GNSS velocity field data during 1999-2007 and the least-squares collocation method (LSCM) are used in this study. Despite the limited stations, after interpolating the GNSS velocity with the LSCM, uncertainties are reduced to some extent during the inversion. Based on the interpolation data, the inversion shows two locked areas that are consistent with the coseismic slip distribution of the Wenchuan earthquake. The third locked area is located on the southern LTB. A checkerboard scheme is proposed, and historic earthquakes larger than M 3.0 since 1950 are analyzed to recheck our inversion. According to the inverted result, the Wenchuan and Lushan earthquakes are two independent events. Additionally, we propose that future destructive earthquakes may occur on the southern segment of the LTB. The maximum magnitude of a future possible earthquake is Mw 8.2.

Automated summary

Fault locking inversion can clarify earthquake occurrence mechanisms and future seismic hazards. However, limited observations in mainland China have resulted in unstable inversions. In this study, GNSS velocity field data and the least-squares collocation method are used to investigate fault locking behavior preceding the 2008 Wenchuan earthquake. After interpolating the GNSS velocity, the inversion shows locked areas consistent with the coseismic slip distribution of the Wenchuan earthquake. Checkerboard scheme and historic earthquake analysis support the inversion results. Future destructive earthquakes may occur on the southern segment of the Longmenshan Thrust Belt with a maximum magnitude of Mw 8.2.