Work

Precise relocation of the 14 August 2021 M w 7.2 Nippes, Haiti, earthquake sequence using broadband and citizen-hosted short-period seismometers

Year: 2025

Type: article

Abstract: On 14 August 2021, the Southern Peninsula of Haiti experienced a M w 7.2 earthquake, 15 years after the devastating M w 7.0 event that struck the capital city of Port-au-Prince on 12 January 2010. We use the data from a local temporary broadband seismic network, a national network of low-cost seismometers, and regional seismic networks, together with a probabilistic, global-search, non-linear location method (NLL-SSST-coherence), to obtain a catalog of 5341 precisely relocated events spanning 20 August 2021 to 6 February 2022, with local magnitudes ranging from 0.5 to 5.6. We compute focal mechanisms for a subset of 73 events through waveform inversion. The catalog can be split into aftershocks directly related to the Nippes earthquake rupture process, and two off-rupture clusters. A first one concerns the Anse-à-Veau–Miragoâne area and corresponds mostly to the aftershock sequence of two M w 5.3 and 4.9 earthquakes that likely activated a segment of the offshore, south-dipping, Jérémie–Malpasse reverse fault system. A second sequence, offshore Jérémie and clustered close to the offshore trace of that same fault, started immediately after the Nippes mainshock and continued during the entire time interval of the present study. The swarm–like temporal distribution of this sequence, as well as evidence for directional propagation of the epicenters, indicate that it was likely driven by fluid migration. We interpret this seismicity as the result of oblique sub-crustal slip on a south-dipping fault which accounts for oblique convergence between the Gonâve and Caribbean plates in southern Hispaniola. Strain in the crust then partitions between reverse faulting on the Jérémie–Malpasse fault system, strike-slip on the Enriquillo fault, and hybrid faulting in between. Seismic hazard assessment for the region should therefore account for faults other than the Enriquillo fault as potential sources for future earthquakes. • Aftershocks are relocated using broadband and low-cost, citizen-hosted, seismometers. • Aftershocks delineate the main event rupture and two off–rupture clusters. • The Anse-à-Veau–Miragoâne cluster activated an offshore reverse fault. • The Jérémie swarm–like cluster was likely driven by fluid migration. • Strain is partitioned on strike-slip, reverse, and obliquely-slipping fault segments.

Source: Tectonophysics

DOI: 10.1016/j.tecto.2025.230982