The New York Times had the expected interesting
article on the Haiti earthquake in its Tuesday science supplement.
I won't copy the article here, but some of the interesting points:
- proximity to the boundaries of the Caribbean plate means natural hazards are expected
- there are two major parallel faults - the Enriquillo and the Septentrional - crossing Haiti in an east-west direction
- the earthquake rupture may actually increase the stress and earthquake probability on adjacent segments of the Enriquillo fault
- the aftershock sequence has been rather active
- there are NO permanent seismograph stations in Haiti
I'd say the article is slightly misleading, although not really wrong, in one respect. It is said that one might have expected a failure on the Septentrional fault, rather than the one that occurred on the Enriquillo. An analogy is that if one were to flip a coin twice, one might "expect" the outcome to be one head and one tails, rather than two heads (or two tails). Indeed, there would be a 50% change of getting one head and one tails, and a 25% chance of getting either two heads, or two tails. Ok, but it would neither be rare nor completely unexpected to get one of the other outcomes. So much of science, including earthquake forecasting, has to do with probabilities, but that is not a concept most people are very comfortable with.
The graphic below, from the article, is quite good. Makes me glad that when I worked in western Jamaica in 1999, on the westward extension of the same fault that was responsible for the Haiti quake, all was seismically quiet, although a major quake hit the area in 1957.
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