The Puerto Rico Trench is an oceanic trench located on the boundary between the Caribbean Sea and the Atlantic Ocean. The trench is associated with a complex transition between the subduction zone to the south along the Lesser Antilles island arc and the major transform fault zone or plate boundary that extends west between Cuba and Hispaniola through the Cayman Trench to the coast of Central America. Scientific studies have concluded that an earthquake occurring along this fault zone could generate a significant tsunami.

The island of Puerto Rico lays immediately to the south of the fault zone and the trench. The trench has a maximum a depth of over 8,400 meters and is the deepest point in the Atlantic Ocean.

Geology

The Puerto Rico Trench is located at a boundary between two plates that pass each other along a transform boundary with only a small component of subduction. The Caribbean Plate is moving to the east while the North American Plate is moving to the west. The North American Plate is subducting the Caribbean Plate to the southeast of the trench. This subduction zone explains the presence of active volcanoes over the southeastern part of the Caribbean Sea. Volcanic activity is frequent along the island arc southeast from Puerto Rico to the Coast of South America.

Puerto Rico, the United States Virgin Islands, British Virgin Islands and the Dominican Republic do not have active volcanoes, however they are at risk from earthquakes and tsunamis.

Public awareness

Knowledge of the risks has not been widespread among the general public of the islands located near the trench, as governments have generally spoken little about the it for two main reasons. First: tourism is essential for those nations to survive; wider knowledge of the danger may cut revenue generated by the industry. Second: the governments want to prevent fear among the local population.

Since 1988, the Puerto Rican Seismic Society has been trying to use the Puerto Rican media to inform people about a future earthquake that could result in a catastrophic tragedy.

Following the 2004 tsunami that affected more than forty countries in the Indian ocean, many more now fear of the consequences that such an event would bring to the Caribbean. Local governments have begun emergency planning. In the case of Puerto Rico and the US Virgin Islands, the United States government which has been studying the problem for years (see this USGS fact sheet from 2001 - PDF) is increasing its seismic investigations and developing tsunami warning systems.

Earthquake history

In 1918, the city of Mayaguez was hit by the Mayaguez earthquake , which is famous in the area, and caused a tsunami. In 1953, Santo Domingo, Dominican Republic was affected by the Santo Domingo earthquake. Experts blame both tragic earthquakes on the Puerto Rico trench fault.

Puerto Rico in particular has always been an area of concern to earthquake experts because, apart from the 1918 episode, there are frequent cases of tremors in and around the island. A 1981 tremor was felt across the island, while another in 1985 was felt in the towns of Cayey and Salinas. The Mameyes slide, which also happened in 1985, killed dozens in the city of Ponce, but was caused by rains from Tropical Storm Isabel and not directly related to seismic activity.

Large earthquakes near Puerto Rico and the Virgin Islands.

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See also

• Plate tectonics
• Caribbean Plate

References

• NOAA Ocean Explorer
• Sound Waves 03 USGS
• Sound Waves 04
• Woods Hole USGS