Simultaneous rupture propagation through fault bifurcation of the 2021
Mw7.4 Maduo earthquake
Abstract
Fault geometric complexity plays a critical role in earthquake rupture
dimension. Fault bifurcations are commonly observed in earthquake
geology, yet, robust kinematic rupture processes on bifurcated fault
branches are largely missing, limiting our understanding of rupture
dynamics and seismic hazard. Here, we holistically study the fault
geometry and bilateral rupture of the 2021 Mw7.4 Maduo, China
earthquake, that shows clear fault bifurcation near its eastern
terminal. We integrate space geodesy imaging, back-projection of
high-frequency teleseismic array waveforms, multiple point source and
finite fault inversions, and constrain in detail the rupture process, in
particular, through its fault bifurcation. Our models reveal a stable
rupture speed of ~2.5 km/s throughout the entire rupture
and a simultaneous rupture through fault branches bifurcated at 20°. The
rupture on bifurcated faults radiated more high-frequency waves,
especially from the stopping phases. The stopping phase on the southern
branch likely stopped the rupture on the northern branch.