Seismic Swarm S20100113.1 Near Grand-Goâve, Haiti

A seismic swarm designated S20100113.1 was recorded 4 km west-southwest of Grangwav (Grand-Goâve), Haiti, between 22:52 UTC on 12 January 2010 and 20:04 UTC on 15 January 2010. Over 69 hours and 11 minutes, 35 earthquakes were detected, with magnitudes between 4.0 and 4.9 and focal depths consistently near 10–11 km.

This activity occurred in the immediate aftermath of the magnitude 7.0 mainshock that struck the same region on 12 January 2010. The main event ruptured a segment of the Enriquillo-Plantain Garden fault zone (EPGFZ), a left-lateral strike-slip system that accommodates relative motion between the Caribbean and North American plates at roughly 2 cm per year. The EPGFZ extends across southern Haiti and has produced several destructive earthquakes in the historical record, including events in 1751 and 1770.

The swarm’s location lies within the western rupture zone of the 2010 mainshock, where afterslip and stress redistribution are known to trigger secondary seismic sequences. All recorded events exhibited shallow crustal depths consistent with the regional tectonics, and the largest shock reached magnitude 4.9. Such sequences are characteristic of the fault’s behavior following major ruptures, reflecting continued adjustment along strike-slip segments and subsidiary structures.

Geological mapping and paleoseismic studies indicate that the EPGFZ has remained active throughout the Holocene, with recurrence intervals for large earthquakes estimated in the range of several hundred to a few thousand years. The 2010 sequence highlighted the fault’s capacity for both primary rupture and prolonged aftershock swarms, underscoring the seismic hazard along Haiti’s southern peninsula.

No comparable swarms have been identified in the instrumental catalog for the region since 2000, confirming the exceptional nature of the January 2010 activity.

References

USGS Earthquake Hazards Program – 2010 Haiti Earthquake
Global Earthquake Model – Caribbean Tectonic Framework
SeismoSight internal swarm classification S20100113.1