Kinematic Rupture Process and Its Implication of a Thrust and Strike-Slip Multi-Fault during the 2021 Haiti Earthquake

Abstract

A devasting Mw7.2 earthquake struck southern Haiti on 14 August 2021, leading to over 2000 casualties and severe structural failures. This earthquake, which ruptured ~70 km west of the 2010 Mw7.0 event, offers a rare opportunity to probe the mechanical properties of southern Haiti. This study investigates the kinematic multi-fault coseismic rupture process by jointly analyzing teleseismic and interferometric synthetic aperture radar (InSAR) datasets. We determined the optimal dip of different segment faults through finite-fault inversion, and the results show that the dips of the first, second and third faults are 62°, 76° and 76°, respectively, coinciding with the relocated aftershock distribution. The results estimated from our joint inversion revealed that the slip was dominated by reverse motion in the first segment and strike-slip motion in the second and third segments. Three slip patches were detected along the strike, with a peak slip of 3.0 m, and the rupture reached the surface at the second segment. The kinematic rupture process shows a unilateral rupture with a high centroid rupture velocity (5.5 km/s), and the rupture broke through the stepover and caused a cascade rupture. The rupture front experiences a directivity pulse of high ground motions with high amplitude and short duration, which may be an additional factor explaining the many landslides concentrated on the western end of the fault. The Coulomb failure stress change result indicates the increases in the probability of future events to the east and west of the 2021 main shock.