Earthquake magnitude is controlled by where and when rupture propagation stops. Yet rupture arrest has rarely been directly observed in near-field seismic records of natural earthquakes. Here we present systematic near-field observations of ground-motion stopping phases from large strike-slip earthquakes. Analysis of 12 global events shows that transient overshoot in fault-parallel ground surface displacement is a robust diagnostic signature of abrupt termination of rupture propagation. Dynamic rupture simulations reveal that near-field ground motions are strongly amplified by low wavespeed rocks at shallow depth, which enhance the amplitude of displacement overshoot recorded at the surface. The occurrence of stopping phases at near-fault locations far from mapped rupture termini implies that large strike-slip earthquakes rupture in a segmented manner, with dynamic rupture propagation punctuated by abrupt arrest and reinitiation at internal fault-segment boundaries.
Kearse et al. (Thu,) studied this question.