Seismic Swarm S20220125.1 in the Haiti Region: January 2022

A notable seismic swarm designated S20220125.1 occurred in the Haiti region from 13:16 on 24 January 2022 to 18:54 on 30 January 2022. Over this 149-hour, 38-minute period, 79 earthquakes were recorded. The events clustered along known tectonic structures, with magnitudes ranging from 2.9 to 5.3 and focal depths predominantly between 1 km and 20 km.

The swarm initiated with a 5.3-magnitude event at 10 km depth, followed rapidly by additional shocks including a 5.1-magnitude quake at similar depth. Subsequent activity featured multiple events above magnitude 4.0, such as a pair of 4.5-magnitude earthquakes on 26 January at 10 km depth and a 4.4-magnitude shock on 29 January at 13 km. Shallower events, some as shallow as 1–2 km, interspersed throughout, indicating possible involvement of near-surface fault segments. Activity tapered after 29 January, concluding with a final 3.2-magnitude event on 30 January.

This swarm aligns with Haiti's position at the complex boundary between the Caribbean and North American tectonic plates. The primary structural feature is the Enriquillo-Plantain Garden fault zone, a left-lateral strike-slip system that accommodates eastward motion of the Caribbean plate relative to the North American plate at rates of approximately 20 mm per year. Historical rupture along this zone produced the devastating 12 January 2010 magnitude-7.0 earthquake, which caused extensive damage in Port-au-Prince and surrounding areas due to its shallow depth and proximity to urban centers.

Seismic swarms represent episodic clusters of events without a single dominant mainshock-aftershock sequence. In the Haiti region, such activity often reflects stress redistribution along segmented faults. According to internal classification records, only two prior swarms have been documented since 1 January 2000: one in 2010 and another in 2021. These episodes underscore the persistent seismic hazard in a setting where accumulated strain can release in both swarm-like sequences and larger individual earthquakes.

The January 2022 swarm contributed to ongoing monitoring efforts by highlighting active fault patches at depths commonly associated with brittle failure in the upper crust. Depths clustered around 10 km for many larger events, consistent with the typical seismogenic zone thickness in this tectonic environment. Shallower foci may indicate fluid involvement or subsidiary fractures.

Continued vigilance remains essential given the region's tectonic setting. Integration of swarm data with regional fault models aids in refining probabilistic seismic hazard assessments for Haiti and neighboring Caribbean nations.

References:
USGS Earthquake Hazards Program – Tectonic setting of Hispaniola
Global CMT Catalog – Fault mechanisms along the Enriquillo-Plantain Garden zone
Internal SeismoSight classification records for swarm parameters