No damage reported after magnitude-4.6 earthquake


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ST. THOMAS - Local agencies reported no damage from the magnitude 4.6 earthquake that shook the territory Tuesday night.

Residents on St. Thomas seemed to feel it the most, according to V.I. Territorial Emergency Management Agency spokeswoman Christine Lett, though residents throughout the territory reported feeling and hearing the moderate quake.

"There were no falling objects, no injuries and no reports of damage," Lett said.

The quake took place at about 11:05 p.m. Tuesday. It was located about 30 miles from St. Thomas, 73 miles from St. Croix, 37.5 miles from St. John and 30.8 miles from Water Island, according to an immediate VITEMA report.

The earthquake was about 24 miles beneath the earth's surface, VITEMA reported.

Seismologists could not pinpoint which tectonic plates were responsible for the rumble in the islands late Tuesday because the quake was not significant enough.

"It wasn't large enough to create a finite fault model," said Julie Dutton, a geophysicist for the U.S. Geological Survey based out of Golden, Colo.

The quake could have been caused by a number of scenarios, as no fewer than four tectonic plates - including the North America, South America, Nazca and Cocos plates - surround the Caribbean plate.

The faults between the plates have transform, or pull-apart, tectonic tendencies, according to the U.S. Geological Survey.

The Puerto Rico Trench zone, where the North America plate slips beneath the Caribbean plate, is an extremely active area.

The trench zone commonly experiences earthquakes, as does the entire region, but the Puerto Rico subduction zone is "thought to be capable of generating a megathrust earthquake," a U.S. Geological Survey report said of the zone. There have been no such events in the last century, according to the federal agency.

The last probable megathrust fault event in that immediate area occurred on May 2, 1787, and was widely felt throughout Puerto Rico, with documented destruction across the entire northern coast, including in Arecibo and San Juan, according to the U.S. Geological Survey.

Since 1900, the two largest earthquakes to occur in this region were the 8.0 Samana earthquake in northeastern Hispaniola on Aug. 4, 1946, and the 7.6 Mona Passage earthquake on July 29, 1943. Both of those earthquakes were shallow thrust fault seismic events.

A significant portion of the motion between the North America plate and the Caribbean plate in this region is accommodated by a series of left-lateral strike-slip faults that bisect the island of Hispaniola, notably the Septentrional Fault in the north and the Enriquillo-Plantain Garden Fault in the south.

Activity adjacent to the Enriquillo-Plantain Garden Fault system is best documented by the devastating 7.0 Haiti strike-slip earthquake and its associated aftershocks on Jan. 12, 2010.

The island of Guadeloupe was the site of one of the largest megathrust earthquakes to occur in this region on Feb. 8, 1843, with a suggested magnitude greater than 8.0. The largest recent intermediate-depth earthquake to occur along the Lesser Antilles arc was the 7.4 Martinique earthquake northwest of Fort-De-France on Nov. 29, 2007.

- Contact Jenny Kane at 714-9102 or email jkane@dailynews.vi.

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