Search

Abstract Earthquake ruptures along a single fault or along a connected system of faults are generally assumed to progress continuously. However, our analysis of the 2023 M7.8 Türkiye earthquake, using finite-fault joint source inversion, uncovered the occurrence of discontinuous rupture jumps. The main fault area adjacent to the splay fault where the earthquake started, and the deeper portion of the northeastern main fault segment exhibited triggered slip before the main rupture front arrived. Through seismic centroid analysis and finite-fault inversion, we estimated apparent rupture speeds within these slip patches reach approximately 6.0 km s-1, exceeding local S-wave velocity. The dynamic triggering mechanism induced the jumping rupture in these areas, resulting in an apparent rupture velocity surpassing the local shear wave velocity. These findings demonstrate the importance of dynamic triggering in adjacent fault systems during large earthquakes, influencing the extent and complexity of rupture propagation.

Abstract Nearby faults interact through stress changes induced by fault slip and viscoelastic flow. The process is, however, often elusive and can be geometry-dependent and time-variant. Here, we combine geodetic and field observations to characterize the interaction of two head-to-head, conjugate faults in eastern Taiwan during the 2022 Chihshang earthquake sequence. We map the coseismic slip on the Central Range fault and dynamically-triggered shallow slip on the Longitudinal Valley fault, which has been creeping interseismically. Overlapping of seismic and aseismic slip suggests that the Longitudinal Valley fault is capable of hosting a variety of distinct slip behaviors. Moreover, substantial slip on the Central Range fault suppresses Coulomb stress on the Longitudinal Valley fault, and vice versa, resulting in seismic bursts in an out-of-phase pattern on the two faults as seen in the hundred-year historical records. Such fault interaction implies the need for time-dependent seismic hazard reassessment for the complex fault system.