Moderate earthquake hits Eastern Caribbean; No tsunami threat

The magnitude 4.8 earthquake struck the Caribbean at 10:59 p.m. local time tonight. Image: USGS

The USGS in the United States and the University of the West Indies Seismic Research Center report that a moderate 4.8 earthquake struck the Eastern Caribbean not long ago. The earthquake struck at 10:59 p.m. local time about 75 miles northwest of Port of Spain, Trinidad and Tobago and about 75 miles southwest of St. George’s in Grenada. The epicenter is about 67 miles northeast of the coast of Venezuela, with the town of Carupano being the closest town in Venezuela to the earthquake. The earthquake struck at a depth of 42 miles.

It does not appear that the earthquake was strong enough to generate a tsunami; as such, there is no tsunami threat to the Caribbean or the east coast of the United States at this time.

There is no tsunami advisory in effect at this time as a result of this earthquake.
There is no tsunami advisory in effect at this time as a result of this earthquake.

Tsunamis are giant waves caused by earthquakes or volcanic eruptions under the sea. In the depths of the ocean, tsunami waves do not increase significantly in height. But as the waves travel landward, they build up to higher and higher heights as the depth of the ocean decreases. The speed of tsunami waves depends on the depth of the ocean rather than the distance from the source of the wave. Tsunami waves can travel as fast as jet planes over deep water, only slowing when they reach shallow water. While tsunamis are often called tidal waves, this name is discouraged by oceanographers because tides have little to do with these giant waves.

The Eastern Caribbean is an example of an island arc system formed at the boundary of a convergent plate. In this case, there is a subduction zone where two plates meet, with the denser plate being forced under the lighter one. With this dynamic activity, earthquakes and volcanoes can become quite common in this part of the world.

Most earthquakes that occur in the Eastern Caribbean are of tectonic or volcanic origin. Tectonic earthquakes are generated when the plates move and the accumulated energy is released in the form of shaking of the ground. As magma moves through the earth’s lithosphere, volcanic earthquakes can occur. In this case, because the magma is less dense than the rock it surrounds, it rises to the surface, breaking up the rock as it moves. When these rocks break, earthquakes are generated.

Last April, the Eastern Caribbean experienced a major volcanic eruption. La Soufrière burst on Saint-Vincent; it is the only active volcano on this Caribbean island.

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