Tuesday, 24 January 2012

Earthquake in the Dominican Republic.

At about 4.50 am local time (8.50 pm GMT), on Monday 23 January 2012 an Earthquake measured as 5.1 on the Richter Scale by the United States Geological Survey and 5.4 on the Richter Scale by the Universidad Autónoma se Santo Domingo, hit the town of Rio San Juan, on the North Coast of the Dominican Republic. The quake occurred at a depth of about 7.4 km, which means it should have been felt quite strongly in the town. There are no reports of any damage or casualties, but workers from the country's Emergency Operations Center are making door-to-door enquiries to look for injured persons who may not have been able to call for help.

Map from the United States Geological Survey showing the level of shaking local populations are likely to have been exposed to.

The Dominican Republic forms the eastern part of the island of La Hispaniola, in the Greater Antilles. The western part of the island is occupied by Haiti, a nation that was devastated by a quake with a magnitude of 7.o on the Richter Scale in 2010, and which still has not recovered. The island has a complex geological structure, with parts of it lying on three different tectonic plates, and two plate margins running east-to-west across the island.

The northernmost part of the island lies on the North American Plate. This is divided from the Gonâve Microplate by the Septentrional Fault Zone, which runs through Rio San Juan, along the north coast of the Dominican Republic and Haiti, then across the Windward Passage and along the south coast of Cuba. The Gonâve Microplate is moving east relative to the North American Plate, pushed by the Mid-Cayman Spreading centre to the west of Jamaica.

To the south the Gonâve Microplate is separated from the Caribbean Plate by the Enriquilo-Plantain Garden Fault Zone, which runs across Southern Haiti and the Dominican Republic, and was the source of the 2010 quake. To the west the fault runs through central Jamaica. The Caribbean Plate is rotating clockwise, effectively moving east relative to the Gonâve Microplate.

Map of the Gonâve Plate, from Wikipedia.

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