Saint Vincent and the Grenadines

Saint Vincent and the Grenadines include one of the Eastern Caribbean's most active volcanoes — La Soufrière on Saint Vincent — making the island's seismicity a blend of subduction-driven tectonic earthquakes and volcano-tectonic events tied to the volcanic system's state of activity. The Lesser Antilles [[subduction-zone]] lies approximately 150 kilometres to the east, where the North American oceanic plate dives beneath the Caribbean Plate, generating the regional seismic background. La Soufrière, rising to 1,234 metres at the island's northern end, has erupted multiple times in recorded history and generates persistent hydrothermal and volcanic seismicity between eruptive episodes. Volcanic earthquake swarms are a regular feature of the island's seismicity and serve as a primary monitoring tool for assessing eruptive potential. The Grenadine islands to the south, being older and less volcanically active, experience mainly the regional subduction seismicity.

La Soufrière has produced several major eruptions in the past two centuries, each preceded and accompanied by significant seismicity. The 1902 eruption killed approximately 1,680 people — an event that occurred on the same day as the catastrophic Mt. Pelée eruption in Martinique. The 1979 eruption, better monitored, was preceded by days of felt volcanic earthquakes and enabled largely successful evacuation of the northern danger zones with no direct eruption deaths. The 2021 eruption of La Soufrière, which began with a months-long swarm of earthquakes in late 2020 and escalated to explosive activity on 9 April 2021, forced the evacuation of approximately 16,000 residents from the red zone; the eruption sequence included multiple explosive blasts generating pyroclastic flows and significant ashfall. The tectonic subduction seismicity produces felt events every few years; the 2007 Martinique earthquake (magnitude 7.4) was strongly felt in Saint Vincent.

The geological character of Saint Vincent is dominated by the constructional volcanic pile of La Soufrière and the older deeply eroded volcanics that form the rest of the island. The volcano sits directly above the subducted North American plate, where slab-derived fluids trigger partial melting in the overlying mantle wedge, generating the andesitic to basaltic andesite magmas that feed eruptions. The relationship between [[subduction-zone]] seismicity and volcanic system pressurisation is monitored by the University of the West Indies Seismic Research Centre, which maintains seismometers and GPS instruments on Saint Vincent as part of the regional network. Magma ascent and degassing generate distinctive patterns of [[seismic-wave]] frequency and amplitude that can be distinguished from tectonic earthquakes, providing the primary basis for eruption forecasts. The 2020–2021 pre-eruptive swarm demonstrated the value of this monitoring in enabling timely public warning.