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Quake expert comments on Haiti
(13 January 2010)
Following the earthquake that hit Haiti, expert Prof Roger Searle explains more about the quake.
Prof Searle, from the Earth Sciences Department, said: “This quake was magnitude 7, equivalent to the energy release of about half a megaton of TNT. Earthquakes of this size can cause relatively slight damage in well-designed and constructed buildings, but considerable destruction in poor ones.
“The last major earthquake in this part of Haiti was 1860; in 1692, a major earthquake in Jamaica caused 2000 deaths. To date (1400GMT Jan 13) the USGS has recorded 33 aftershocks greater than magnitude 4.5 (large enough to cause at least minor damage).
“Earthquakes are complex processes that are very hard to predict. The earth’s crust is a complex system and at the boundaries of the tectonic plates there are networks of faults separating lots of smaller blocks. As the plates move, stress gradually builds up until one part of this complex system gives way, and an earthquake occurs. It’s a little bit like building a pile of stones: it gets steeper and steeper, and eventually the whole thing will give way, but it’s very hard to say just when and where. We can actually predict reasonably well where earthquakes will occur, but not when.
“Once an earthquake has occurred, we can calculate how that will affect the stress in the surrounding region: faults where the stress has increased are most likely to be the next to slip.”
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