The sliding friction coefficient and the strong earthquake recurrence interval of the Longmenshan fault zone revealed by numerical simulations

Following the Wenchuan M_S8.0 earthquake, numerous studies have sought to determine the sliding friction coefficient of the Longmenshan fault (LMSF) zone. However, results have varied widely (0.02-0.61), deviating significantly from traditional understandings (0.6-0.85). As a critical parameter governing fault strength, the sliding friction coefficient influences coseismic stress drop and the recurrence interval of large earthquakes. To better constrain this coefficient, we constructed a two-dimensional finite-element contact model extending 300 km in length and 104 km in depth that includes the LMSF. Constrained by GPS observations, we controlled fault activity using static and dynamic friction constitutive relations, and conducted multiple numerical simulations by assigning different sliding friction coefficients to the fault to simulate regional deformation and the recurrence of strong earthquakes. Comparison between the simulation results and observational data, along with lateral comparisons across different simulation results, allowed us to constrain the sliding friction coefficient of the LMSF. The main conclusions are as follows: the LMSF exhibits a relatively low sliding friction coefficient around 0.08. The recurrence interval for magnitude 8.0 earthquakes on the LMSF is approximately 5460 ±130 years. Coseismic shear stress drop is a key factor in controlling the spatial distribution of mainshocks and aftershocks. Additionally, the rapid uplift along the eastern Qinghai-Xizang Plateau is likely driven by upper mantle creep beneath the Songpan-Garzê block.