A geologist’s perpective on the Port-au-Prince earthquake

My colleague at Vassar, Brian McAdoo, an expert on tsunamis, posted the following on his blog, “The Tsunami Project.” I am including it here, since it gives us a scientific perspective on the earthwuake and the reasons it has been such a devastating event:

The M=7.0 earthquake that struck Haiti was, and will remain, an unprecedented disaster for this hemisphere. As of today, Monday 18 July 2010, it looks as if upwards of 100,000 people will have died, with millions displaced. It will take years to get Haiti back to even the sorry state that existed prior to this earthquake.
There are several reasons why this earthquake became a disaster. Most of those reasons were not geophysical-
1. The earthquake was not that big- a M=7.0 earthquake struck the San Francisco Bay Area in 1989 and killed 63 people. But that earthquake also caused ~$6 B in economic losses. When a disaster strikes wealthy countries, the largest losses are felt in the economy. When disaster strikes in poor countries, the losses are in human lives.
2. It is exceedingly difficult for an earthquake to kill a person. Perhaps someone with a pre-existing condition would suffer a massive heart attack and die. Earthquakes can generate landslides and tsunamis that certainly can be lethal. But what killed every single person in Haiti was poor construction.
3. Adding to the poor construction is the fact that Port-au-Prince, like almost all cities, is build on flat ground- in this case, and alluvial (river) plain. The sediment that make up this type of land are not really rock- when they shake with an earthquake, they move around a lot, and buildings cannot stand that much movement. Luckily for Haiti, there was not as much land reclamation as there is in many developed regions like San Francisco’s Marina District and Singapore.
4. And the last thing that conspired to doom Port-au-Prince is a long and sordid post-colonial history. Following a successful slave revolt- the second independence movement in the Western Hemisphere- Haiti suffered from 200 years of neglect- from plain-and-simple racism in the 19th century to poor governance with the Duvalier’s in the 20th century. And then to really finish off the picture of neglect, the privatization, deregulation and neglect that comes with neoliberalization left the care of the people in the hands of… of… Well, nobody.
Thankfully, this earthquake occurred on a strike-slip or transform fault, where two plates slide past each other. This type of fault does not produce the same degree of land-level changes that reverse and normal faults do, where one plate moves up or down relative to the other. That said, I have heard reports of the seafloor being uplifted west of Port-au-Prince. There have been tsunamis in this region- in fact, this earthquake could have triggered a submarine landslide which could have in turn generated a tsunami. As land-use degradation associated with wholesale deforestation of the Haitian landscape continues, more sediment will be washed down rivers into the offshore, increasing the risk of a landslide-generated tsunami. In fact, an earthquake in 1692 on the same fault generated a tsunami in the Jamaican capital of Kingston.
This earthquake should be a wake-up call for Kingston. Should the 1692 earthquake happen today, Kingston would be devastated, albeit not to the same degree as Port-au-Prince. If these strong-shaking events occur in regions with poor construction, after the earthquake is done wreaking its havoc, the tsunami will finish the job, leaving little hope for those stuck in the collapsed buildings.
An earthquake is not a disaster. To understand a disaster, you need to take into account the geophysics of the earthquake, to be sure, but you must also consider why the disaster-stricken area was so vulnerable. This is related to the foundations of the region- both geological, historical, economic, socio-cultural, and ecological. Disasters are complex beasts, and the Tsunami Project hopes to bring these diverse stakeholders to the table to begin unravelling the complexities to mitigate against the next, inevitable events.

Originally posted at http://tsunamiproject.ning.com/profiles/blogs/haiti-at-least-there-was-no

2 thoughts on “A geologist’s perpective on the Port-au-Prince earthquake

  1. are what i think is known to be called techtonic plaques situated ruffly in the same areas as the ribons that determine hot and cold and fresh and salted water in the same place ? and does this not point to serious consequences of mother nature (natural course) and global warming put together a detriment to the most vunerable.

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