Aftershock Triggering Mechanism by the 7 January 2025 Mw 7.1 Tingri Earthquake

Abstract The Mw 7.1 Tingri earthquake represents the largest normal-faulting event within the Lhasa block since 1952. This rupture occurred along the approximately north–south-trending Dengmocuo rift, which constitutes the seismogenic fault. The event provides an exceptional case study to examine aftershock distribution patterns and triggering mechanisms following large normal-fault earthquakes in the Tibetan plateau. We calculated Coulomb failure stress changes (ΔCFS) induced by coseismic slip and postseismic poroelastic rebound using a coseismic slip model inverted from Interferometric Synthetic Aperture Radar and strong-motion records. The earthquake rupture propagated ∼40 km north of the mainshock hypocenter, with slip predominantly confined to the upper 10 km of the crust. Such ruptures typically produce stress loading at the fault’s northern and southern termini while generating stress-shadow zones along the eastern and western flanks. Within this pattern, the main rupture zone spatially coincides with the stress-shadow zone, whereas adjacent regions constitute CFS loading zones. Postseismic fluid migration induces significant CFS loading within the main rupture zone, effectively compensating for coseismic stress shadows and subsequently triggering peripheral aftershocks. The triggering mechanisms of aftershocks vary significantly across different segments of the fault system. Coseismic slip accounts for only 44% of total aftershock triggering, whereas poroelastic rebound contributes a notably higher proportion, reaching up to 65%, particularly in the northern segment, where it peaks at 74%. This indicates that postseismic fluid migration has a significant impact on the occurrence of aftershocks in the main rupture zone.