Variable Mechanisms of Supershear Rupture During the 2001 Mw 7.8 Kunlun Earthquake

Abstract Investigating the mechanisms of supershear rupture helps to better understand earthquake physics. The 2001 Mw 7.8 Kunlun earthquake was one of the largest continental supershear events, but the mechanism of supershear remains unexplained. Here, we construct dynamic rupture models that incorporate heterogeneous stress and frictional parameters, constrained by geodetic and geological data, to simulate the rupture process. The results show that the supershear rupture initiates at ∼49 s and propagates for ∼20 km over three seconds, which is primarily controlled by the Burridge–Andrews mechanism. After passing through a low-stress barrier, from 53 to 61 s, the rupture velocity gradually increases with the generation of a new crack ahead of the rupture tip that propagates at supershear speed. The rupture then evolves into a sustained supershear rupture driven by a free-surface-induced mechanism, which persists for ∼180 km before decelerating into subshear rupture, with the entire supershear phase lasting ∼47 s. Our findings highlight the coexistence of multiple rupture mechanisms during one earthquake, that is, supershear rupture could be driven by different mechanisms at different stages, which offers new insights into earthquake dynamics.