Crustal Rheology and Fluid Migration Control the 2008 Mw 7.9 Wenchuan, China, Earthquake

The 2008 Mw 7.9 Wenchuan earthquake caused widespread devastation, prompting in-depth investigations into its underlying mechanisms. Benefiting from the dense seismograph deployments of the ChinArray project, we conducted an innovative Wasserstein-based full-waveform inversion in the Longmenshan region. Our results reveal significant rheological contrasts across the region: a mechanically weak plateau west of the Longriba fault (LRBF), characterized by low-seismic velocity and high-Poisson’s ratio; a moderately stronger zone between the LRBF and Longmenshan fault (LMSF), exhibiting intermediate velocity and low-Poisson’s ratio; and a highly rigid Sichuan basin with high velocity and low-Poisson’s ratio. This rheological architecture suggests enhanced crustal strength surrounding the LMSF, facilitating significant strain accumulation prior to rupture. Notably, the elevated Poisson’s ratio beneath the earthquake’s hypocenter indicates fluid-rich zones, where the migration of fluids into the seismogenic zone may have increased the likelihood of mainshock fault failure. These findings provide new insights into the physical mechanisms driving the Wenchuan earthquake and offer broader implications for understanding the generation of devastating earthquakes worldwide.