Magnitude 6.4 Earthquake Rocks Puerto Rico

MIAMI, Florida -- The U.S. Geological Survey (USGS) is reporting that an earthquake of around Magnitude 6.4 has hit 61 miles northwest of San Juan, Puerto Rico at 04:01 a.m. Universal Time (11:01 a.m. Eastern Time) on Monday, January 13, 2014.  The epicenter was 35.4 miles north of Hatillo, Puerto Rico and 17.4 miles deep.

According to the USGS, the earthquake occurred as a result of oblique-thrust faulting. Preliminary faulting mechanisms for the event indicate it ruptured either a structure dipping shallowly to the south and striking approximately east-west, or a near-vertical structure striking northwest-southeast. 

At the location of this earthquake, the North America plate moves west-southwest with respect to the Caribbean plate at a velocity of approximately 20 mm/yr, and subducts beneath the Caribbean plate at the Puerto Rico Trench.  The location, depth and mechanism of the earthquake are consistent with the event occurring on this subduction zone interface. 

While the Puerto Rico Trench is known to be a significant seismic hazard, and is capable of hosting M8+ earthquakes, moderate-to-large events on the subduction zone are rare. 

The National Weather Service in Miami issued a statement that there is no tsunami threat (also known as a tidal wave or seismic wave) to Florida as a result of this earthquake. 

The Puerto Rico earthquake comes on the heels of a 5.1 magnitude earthquake that shook Cuba and was felt in Florida four days earlier.