Saint Kitts and Nevis

Saint Kitts and Nevis sit on the northern volcanic arc of the Lesser Antilles, where the North American Plate descends beneath the Caribbean Plate along the Lesser Antilles [[subduction-zone]]. Both islands are dominated by active or recently active volcanic centres: Mount Liamuiga on Saint Kitts and Nevis Peak on Nevis are both considered potentially active stratovolcanoes, and their volcanic systems generate hydrothermal and volcano-tectonic earthquakes as well as the background seismicity from the subduction process beneath. The convergence rate is approximately 2 centimetres per year, modest compared to faster subduction zones, but the shallow locked interface and the proximity of active volcanic systems combine to create a seismic environment where both tectonic and volcanic earthquake sources are relevant. [[tsunami]] exposure from great earthquakes on the Puerto Rico Trench to the north is a recognised long-term hazard.

Historical records from the colonial period document significant felt earthquakes in Saint Kitts. The 1843 Guadeloupe earthquake (estimated magnitude 8.0) caused significant damage in Saint Kitts. A 1974 Antigua area earthquake was felt strongly. The 8 December 2004 earthquake near Antigua (magnitude 6.1) was felt in Saint Kitts and Nevis with minor structural effects. Volcanic earthquake swarms have been recorded at both Liamuiga and Nevis Peak without leading to eruptions. The University of the West Indies Seismic Research Centre monitors the Eastern Caribbean and publishes regular seismicity bulletins for the region. Overall, Saint Kitts and Nevis face moderate seismic hazard with the principal risk concentrated in the volcanic-tectonic interface and the occasional larger subduction event from the regional arc system.

The geology of both islands is entirely volcanic; the Precambrian or Paleozoic continental basement found on some other Caribbean islands is absent beneath the Lesser Antilles volcanic arc. Both islands are composed of Pliocene and Pleistocene andesitic and dacitic volcanic materials that form the steep stratovolcano cones visible from the sea. The carbonate coastal lowlands of southern Saint Kitts represent younger marine deposits overlying the volcanic flanks. The Lesser Antilles arc formed as the North American oceanic crust began subducting beneath the Caribbean Plate roughly 40 million years ago, and the volcanic arc has remained active since that time. The relationship between [[subduction-zone]] seismicity and volcanic system reactivation is an active area of monitoring concern: large interface earthquakes can perturb magma chambers and potentially trigger volcanic unrest.