Offshore Virgin Islands earthquakes (5-6 February 2021)

This map shows the distribution of earthquakes that hit offshore from the Virgin Islands in the western Atlantic Ocean starting late on 5 February 2021 and continuing into 6 February. These include a main event, a magnitude 5.0 earthquake that occurred at 3:05 AM, local time, on 6 February 2021, plus foreshocks and aftershocks. As of this writing, 22 earthquakes have occurred - most are aftershocks. The epicenter of the main event was about 65 kilometers northwest of Anegada Island (= the arc-shaped island at far-right on the map). The hypocenter was about 78 kilometers deep.

These are subduction zone earthquakes. Subduction zones have a tectonic plate composed of oceanic lithosphere diving underneath a plate of continental or oceanic lithosphere. In this case, oceanic lithosphere of the North American Plate is subducting westward under the Caribbean Plate. Subduction zones have the most powerful tectonic quakes in the world. Quakes and volcanism are common geologic hazards in such settings. Here, the subduction zone itself is a deep seafloor trough called the Puerto Rico Trench.

See info. at:
earthquake.usgs.gov/earthquakes/eventpage/pr2021037002/ex...
and
earthquake.usgs.gov/earthquakes/eventpage/pr2021037002/re... [Scroll down for a tectonic summary of the Caribbean region.]
and
earthquake.usgs.gov/earthquakes/tectonic/images/caribbean...
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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

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Taken on: February 6, 2021

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Sets appears in: • 2021 Earthquakes • Aftershocks more » • Caribbean & Lesser Antilles area Earthquakes • Earthquakes « less

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