Coseismic Rupture and Aftershock Migration Governed by Multiple Fault Geometries: The 2022 Mw 6.6 Menyuan Earthquake

Abstract Multiple fault geometries, including stepovers and variations in strike and dip angles, play a crucial role in controlling seismic processes. Previous studies have examined individual geometric factors, but integrated analyses of how they jointly govern seismic sequences remain limited. The 2022 Mw 6.6 Menyuan earthquake, located within a complex strike-slip fault system in the northeastern Tibetan Plateau, presents a valuable case study. Here, we combine a high-resolution seismic catalog (∼4200 events) with an Interferometric Synthetic Aperture Radar-derived coseismic slip model to elucidate these controls. Our results reveal a multigeometry fault system involving the Tuolaishan fault and the Lenglongling fault, characterized by distinct fault discontinuity features such as fault stepovers, bends, and variations in strike and dip. We observe an aftershock gap of ∼5 km at the fault bend, for which the fault’s strike and dip change by ∼10° to 14°. We demonstrate that these interacting geometries played a dominant role in the coseismic and postseismic process: the coseismic surface rupture successfully propagated across a ∼2.5 km stepover but was arrested by the aftershock gap. Meanwhile, the multiple geometries acted as stress concentrators, which likely localized the peak slip to ∼3.5 m—an anomalously high value, 2–3 times larger than typical for an Mw 6.6 event. Postseismically, the aftershocks evolved as two independent fronts separated by the variations in strike and dip (fault bend). The detection of repeating earthquakes and the observed “W-shaped” logarithmic migration pattern indicates that aseismic slip and fault discontinuities collectively dominate the path of aftershock expansion. These findings highlight that multiple geometries act as both rupture barriers and stress amplifiers, significantly elevating local seismic hazards.