Examining Stress Interactions Among Three Major Earthquakes on the Longmenshan Fault, Sichuan, China: Insights from Coulomb Stress Change and Seismicity Analysis

: On June 1, 2022, a M S 6.1 earthquake struck Lushan County, Ya'an City, Sichuan Province, China. This event constitutes another major earthquake in the Longmenshan Fault Zone (LMFZ), following the 2008 Wenchuan M S 8.0 earthquake and the 2013 Lushan M S 7.0 earthquake. To investigate the potential triggering relationships among these three major events, we integrated two analytical approaches: seismicity rate change detection based on the space-time Epidemic-Type Aftershock Sequence (ETAS) model, and Coulomb stress change (Δ CFS ) calculation. Our seismicity analysis indicates that the background rate of M S ≥4.0 earthquakes in the Lushan region increased significantly after the 2008 Wenchuan earthquake but decreased subsequent to the 2013 Lushan event. Regarding Coulomb stress, the coseismic stress change induced by the 2008 Wenchuan earthquake at the hypocenter of the 2022 Lushan earthquake was negligible. However, the cumulative Coulomb stress increased substantially over the following 14 years due to viscoelastic relaxation. The Δ CFS caused by the 2013 Lushan earthquake is highly dependent on the adopted model. Synthesizing these findings, we infer that the 2008 Wenchuan earthquake triggered the 2022 Lushan earthquake, with postseismic viscoelastic relaxation playing a crucial role. In contrast, the 2013 Lushan earthquake may have delayed the occurrence of the 2022 event. This study underscores the complex interactions between these three major earthquakes in the LMFZ. The proposed integrated strategy effectively alleviates the inherent model dependence in Δ CFS calculations and provides a robust framework for evaluating seismic hazard and could be applied in other seismic regions.