Seismic Swarm S20220608.2 Near the Coast of Nicaragua

A seismic swarm designated S20220608.2 occurred off the Pacific coast of Nicaragua from 05:54 UTC on 8 June 2022 to 04:13 UTC on 12 June 2022. During this 94-hour period, 55 earthquakes were recorded, with magnitudes ranging from 2.5 to 4.3 and focal depths between 1 and 13 km. The events clustered in a compact offshore area, consistent with shallow crustal or upper-plate seismicity along the Middle America subduction zone.

The swarm initiated with a magnitude 2.5 event at 11 km depth. Activity intensified later on 8 June, culminating in the largest event—a magnitude 4.3 earthquake at 13 km depth at 21:37 UTC. Subsequent events remained predominantly below magnitude 3.5, with most occurring at depths of 5–8 km. The sequence exhibited typical swarm characteristics: a gradual onset, lack of a single dominant mainshock, and steady decay over four days without aftershock-style clustering.

Nicaragua lies at the convergent boundary where the Cocos Plate subducts northeastward beneath the Caribbean Plate at rates of approximately 8–9 cm per year. This tectonic setting produces the Middle America Trench and drives both interplate thrust earthquakes and upper-plate normal or strike-slip faulting. Shallow swarms in this region often reflect fluid migration, stress transfer along the plate interface, or activation of crustal faults linked to the Nicaraguan Depression and nearby volcanic arcs.

Historical records document recurrent seismic swarms and moderate earthquakes along Nicaragua’s Pacific margin. Notable events include the 1992 magnitude 7.7 tsunami earthquake and the 1972 Managua earthquake, underscoring the region’s persistent seismic hazard. Modern monitoring networks operated by INETER and international agencies have catalogued numerous swarms since 2000, frequently associated with the volcanic chain extending from Cosigüina to Ometepe.

The June 2022 swarm did not produce reported damage or felt intensities above IV on the Modified Mercalli scale, reflecting its modest magnitudes and offshore location. Such sequences contribute to ongoing strain accumulation studies and help refine seismic hazard models for Central America’s densely populated Pacific lowlands.

References

• USGS Earthquake Catalog (earthquake.usgs.gov)
• INETER Seismic Bulletins, Nicaragua
• DeMets et al., 2010, Journal of Geophysical Research (plate motion data)