Rupture Geometry and Slip Distribution of the Mw 7.2 Nippes Earthquake, Haiti, From Space Geodetic Data

Abstract

AbstractOn 14 August 2021 the Mw 7.2 Nippes earthquake struck southern Haiti, rupturing a segment of the Enriquillo‐Plantain Garden Fault system (EPGF), a 300 km‐long strike‐slip fault system that accommodates half of the highly oblique convergence displacement between the Caribbean and the North American plates. We use coseismic surface displacements from Interferometric Synthetic Aperture Radar and Global Navigation Satellite System (GNSS) to estimate the geometry of the rupture through a systematic parametric exploration, determine its mechanism, and relate them to the regional tectonics derived from interseismic GNSS measurements. We show that the earthquake ruptured a north dipping fault (66 ± 4° dip) with a geodetically determined moment release that is 40% reverse and 60% strike‐slip. We cannot conclude whether this north‐dipping structure is the EPGF itself or a distinct fault running parallel to the EPGF. The rupture then evolved to the west on a vertical (86 ± 2° dip) fault parallel to the EPGF, the Ravine du Sud fault, with left‐lateral strike‐slip motion. The coseismic slip distribution of the 2010 Léogane and 2021 Nippes earthquakes, consistent with the transpressional interseismic strain rate field, show a segmentation of the Caribbean–North American plate boundary in southern Haiti and imply a revision in our understanding of the mode of earthquake rupture within the EPGF system.