Seismic Swarm PS20100112.1 Near Léogâne, Haiti

The seismic swarm PS20100112.1 occurred 7 km south of Léogâne, Haiti, beginning at 21:53 UTC on 12 January 2010 and concluding at 14:43 UTC on 13 January 2010. Over 16 hours and 50 minutes, 17 earthquakes were recorded, initiating with a magnitude 7.0 event at 13 km depth. Subsequent events ranged from magnitude 4.1 to 6.0, predominantly at 10 km depth, illustrating a rapid succession of aftershocks following the principal shock. This sequence aligns with the well-documented 12 January 2010 mainshock, whose epicenter lay approximately 10 km southeast of Léogâne. The provided event parameters show an initial energetic release succeeded by multiple magnitude 5+ aftershocks within the first hours, including peaks at magnitudes 5.8 and 6.0. Depths clustered near 10–13 km, consistent with shallow crustal faulting in the region. Haiti occupies the northern margin of the Caribbean Plate, where left-lateral strike-slip motion occurs along the Enriquillo–Plantain Garden fault zone (EPGFZ). This fault system accommodates part of the oblique convergence between the Caribbean and North American plates at rates of roughly 2 cm per year. The 2010 sequence ruptured a previously locked segment of the EPGFZ, producing widespread surface deformation and liquefaction in the Léogâne area. Geological mapping confirms the fault’s east–west orientation and its history of infrequent but large earthquakes, with paleoseismic evidence of prior events centuries earlier. A later strong earthquake of magnitude 7.2 struck the Nippes region on 14 August 2021, centered 59 km from the 2010 swarm locus. This event further highlighted the continued seismic hazard along the same fault system, though it occurred on a western segment with distinct rupture characteristics. The 2010 swarm underscores the aftershock productivity typical of moderate-to-large strike-slip events in Haiti’s tectonically active setting. Magnitudes decayed gradually after the first day, yet the high initial rate of M5+ events posed ongoing risk to already damaged infrastructure. Regional seismic monitoring has since improved, aiding better characterization of fault segmentation and recurrence intervals along the EPGFZ. References
USGS Earthquake Hazards Program catalog (events 2010–2021)
Geological Society of America special papers on Caribbean tectonics
Peer-reviewed studies in Geophysical Research Letters on the 2010 Léogâne rupture