The United States Geological Survey recorded a Magnitude 6.4 Earthquake at a depth of 10.0 km roughly 8 km off the south coast of Puerto Rico, slightly before 4.25 am local time (slightly before 8.25 am GMT) on Tuesday 8 Jamuary 2020. The event caused several buidings to collapse, killed at least one person, and injured at least eight more, and comes less than a day after a magnitude 5.8 Earthquake in the same area which collapsed Punta Ventana, or Window Point, a distinctive coastal rock archway popular with tourists, and is the latest in a series of strong tremors in the area that began in late December. The initial Earthquake has been followed by several aftershocks, some of which have been in excess of Magnitude 6.0.
The Inmaculada Concepción church in Guayanilla, Puerto Rico, which partially collapsed following an Earthquake on 8 January 2020. CNN.
Puerto Rico is located at the northeastern fringe of the Caribbean Tectonic Plate. The Atlantic Plate (strictly speaking, an extension of the South American Plate which runs to the northeast of the Caribbean) is being subducted beneath this. The subduction of the Atlantic Plate beneath the Caribbean Plate is not a smooth process, with the two plates constantly sticking together then breaking apart as the tectonic pressure builds up, causing Earthquakes in the process, though since the boundary between the two plates is some way to the north and east of the islands, Earthquakes in this area tend to be both deep and offshore, which lessens their destructive potential.
The subduction of the Atlantic Plate beneath the Caribbean Plate fuels the volcanoes of the Lesser Antilles Volcanic Arc. George Pararas-Carayannis.
Witness accounts of quakes can help geologists to understand these events and the rock structures that cause them. If you felt this quake (or if you were in the area but did not, which is also useful information) you can report it to the USGS here.
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