* Astronomy

Haiti quake: The worst of places for a big tremor

It was immediately obvious that Tuesday's quake in Haiti would be an appalling natural disaster.
This was a large tremor centred on an impoverished country with little recent experience or preparedness for such a major event of this kind.
The simplest concrete structures in the capital of Port-au-Prince will have crumpled under the same strain.
Seismometers recorded a preliminary magnitude of 7.0 at 1653 local time (2153 GMT).
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Microplate tectonics in the northeastern Caribbean


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Title: ENRIQUILLO-PLANTAIN GARDEN STRIKE-SLIP FAULT ZONE: A MAJOR SEISMIC HAZARD AFFECTING DOMINICAN REPUBLIC, HAITI AND JAMAICA
Authors: Mann, Paul, Calais, Eric, Demets, Chuck, Prentice, Carol S., and Wiggins-Grandison, Margaret

he Enriquillo-Plantain Garden fault zone (EPGFZ) extends from south-central Hispaniola to Jamaica and defines the southern edge of the Gonave microplate. The EPGFZ forms a continuous and prominent geomorphic lineament from the Enriquillo Valley of the Dominican Republic , through the southern peninsula of Haiti , across the Jamaica Passage between Jamaica and Haiti and along the Plantain Garden fault zone bounding the southern edge of the Blue Mountains of eastern Jamaica . The linearity of the fault and its association with en echelon folds, pull-apart basins, and restraining bends indicates that motion is left-lateral and late Quaternary in age. Historical earthquakes indicate that the last major ruptures of the fault occurred in an east to west time-space progression that began in 1751 in south-central Hispaniola and perhaps culminated in the Kingston , Jamaica , event in 1907. Recorded seismicity over the past 40 years is sparse as expected from a fully locked fault plane. GPS-constrained block models with elastic strain accumulation give ~8 mm/year of slip rate on the fault. Since the last major event in south-central Dominican Republic was in 1751, that yields ~2 meters of accumulated strain deficit, or a Mw=7.2 earthquake if all is released in a single event today. The two largest cities within 30 km of the fault zone are Port-au-Prince , Haiti , and Kingston , Jamaica , with a combined population of 3.65 million inhabitants. We present initial results from a paleoseismic study of the Jamaica segment of the EGPGFZ conducted in January, 2008, to determine the chronology of its historic and prehistoric ruptures. Such studies should be considered high priority in Jamaica, Haiti and the Dominican Republic given the seismic hazards posed by the fault.

Source

Magnitude 5.1, January 13, 2010 01:16:52 GMT
Magnitude 5.2, January 13, 2010 00:59:06 GMT
Magnitude 5.0, January 13, 2010 00:43:27 GMT
Magnitude 5.1, January 12, 2010 23:12:04 GMT
Magnitude 5.5, January 12, 2010 22:12:05 GMT
Magnitude 5.9, January 12, 2010 22:00:42 GMT