Seismic Swarm S20220107.1: Analysis of Activity Near the Nicaragua Coast

A seismic swarm designated S20220107.1 was recorded near the coast of Nicaragua between 16:28 UTC on 6 January 2022 and 03:25 UTC on 10 January 2022. Over this 82-hour, 56-minute period, 44 earthquakes were detected. The events clustered in a tectonically active offshore region where the Cocos Plate subducts beneath the Caribbean Plate along the Middle America Trench.

The swarm exhibited typical characteristics of subduction-related seismicity, with events distributed across depths of 7 to 30 km. Magnitudes ranged from 2.6 to 5.1, and the majority occurred at intermediate crustal depths consistent with the plate interface and overlying wedge. The largest event, magnitude 5.1, took place at 17:04 UTC on 7 January at a depth of 10 km. Other notable shocks included a magnitude 4.7 event on 6 January at 10 km depth and a magnitude 4.3 event later that day, also at 10 km. Shallower events (under 15 km) were fewer and generally smaller, while deeper activity (25–30 km) dominated the later stages of the sequence.

Geologically, the Nicaraguan margin forms part of the Central American volcanic arc and forearc system. Convergence rates average 8–9 cm per year, producing frequent moderate earthquakes and occasional larger interface ruptures. Historical records document destructive events such as the 1992 Nicaragua tsunami earthquake (Mw 7.7) and the 1972 Managua earthquake (Mw 6.2), both linked to the same subduction dynamics. Swarms like S20220107.1 commonly occur in this setting and are interpreted as localized stress adjustments or fluid migration along the plate boundary rather than foreshock sequences leading to a major rupture.

The spatial and temporal distribution of the 44 events shows an initial burst of activity on 6 January followed by a gradual decline, with isolated larger shocks on 7 January. Depths remained broadly consistent throughout, supporting an origin near the seismogenic zone of the subduction interface. No surface rupture or significant afterslip was reported in association with this swarm.

Such sequences contribute to ongoing monitoring of strain accumulation along the Nicaraguan segment of the trench. Continued seismic and geodetic observations help refine hazard assessments for coastal communities exposed to both strong ground shaking and potential tsunami generation.

References

USGS Earthquake Catalog
Global CMT Catalog
Red Sísmica de Nicaragua (INETER) reports