Earthquake Science

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“…The USGS has already measured more than 40 aftershocks above a 4.0 magnitude (including a 5.9 and 5.5 magnitude) and many more below that, Bedwell said. More aftershocks are anticipated in the coming days and weeks as the restive fault continues to react to the jolt that set it off in the first plac”…”

University of West Indies Earthquake FAQ

According to the Wunderground weather blog Haiti was just now recovering from the 2008 Hurricane season.

“…In many ways, the hurricane season of 2008 was the cruelest ever experienced in Haiti. Four storms–Fay, Gustav, Hanna, and Ike–dumped heavy rains on the impoverished nation. The rugged hillsides, stripped bare of 98% of their forest cover thanks to deforestation, let flood waters rampage into large areas of the country. Particularly hard-hit was Gonaives, the fourth largest city. According to reliefweb.org, Haiti suffered 793 killed, with 310 missing and another 593 injured. The hurricanes destroyed 22,702 homes and damaged another 84,625. About 800,000 people were affected–8% of Haiti’s total population. The flood wiped out 70% of Haiti’s crops, resulting in dozens of deaths of children due to malnutrition in the months following the storms. Damage was estimated at over $1 billion, the costliest natural disaster in Haitian history. The damage amounted to over 5% of the country’s $17 billion GDP, a massive blow for a nation so poor…”

Two years ago this specific quake was predicted.

“...In a presentation to the 18th Caribbean Geological Conference in 2008, the team pointed out that their models showed a slip rate of around 8 millimetres per year on the fault. In their abstract they warned that this, combined with the fact that the last known major earthquake near Haiti was in 1751, could add up to yield “~2 meters of accumulated strain deficit, or a Mw=7.2 earthquake if all is released in a single event today”. One of the team members, geophysicist Eric Calais of Purdue University in West Lafayette, Indiana, said in an e-mail to Nature: “Unfortunately we were pretty much right on.”…”

From Eruptions comes a portal into the science of the big one in Haiti.  This is a straight post about the cold blooded science of the incident – nothing more and nothing less.  This is the largest quake in the region since 1751, when there was one well over 8.0.  This specific quake has now been ramped up to a 7.2, and was quite shallow, which is why there was so much damage.

From Nature:

“…The island of Hispaniola, with Haiti on the western half and the Dominican Republic on the eastern half, lies on the northern edge of the Caribbean tectonic plate. The much larger North American plate moves westward relative to the Caribbean plate. There are two major faults between the plates at this point: the Septentrional fault system, which runs through northern Haiti, and the Enriquillo-Plaintain Garden fault system in the south. This quake seems to have occurred on the Enriquillo-Plaintain Garden fault system, which accounts for nearly half of the overall movement between the Caribbean and North American plates — around 7 millimetres per year, according to the USGS….”

From Science Blogs:

“...The Caribbean is contained on its own separate little plate; a rather diminutive part of the tectonic jigsaw that is the Earth’s crust. It is surrounded on three sides by the much larger North and South American plates, both of which are moving approximately westwards with respect to the Caribbean plate at around 2-3 centimetres a year. On the eastern edge of the plate, the boundary runs perpendicular to the direction of relative plate motion, so there is compression and subduction (and subduction volcanism, exemplified by the likes of Montserrat). However, as the boundary curves around to form the northern boundary of the Caribbean plate, where the Haitian earthquake occurred, it starts to run parallel to the direction of relative plate motion, making strike-slip faulting along E-W trending faults the most likely expression of deformation in this region. This is exactly what the Haitian quake appears to record….”

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