Group items tagged

If you read nothing else (beyond the article and this post), please read the “The Seismic Future of Cities (pdf),” a 2009 paper by  Roger Bilham of the University of Colorado, who just  returned from Haiti and has been roaming the world weighing which cities are most in harm’s way. (Dr. Bilham also wrote an opinion piece on bad construction in quake zones, focused on Haiti, that ran in Nature last week.) He is part of a Greek chorus of  seismologists and earthquake engineers who have been warning for a long time that some of the world’s biggest, fastest-growing cities are “ rubble in waiting,” given the haphazard rush of construction of apartments and workplaces for mainly poor new residents.

The stark reality is that, while earthquakes often capture our attention case by case, we have entered an age where population density and persistent poverty are putting enormous numbers of people in harm’s way.

PARIS - THE magnitude 7.0 earthquake that struck Haiti in January, killing a quarter of a million people, also unleashed a string of tsunamis on the country's western coast, scientists reported on Sunday. Several waves measuring up to 75cm were caused by a combination of earth movement and coastal landslides. They included banks of sediment on the sea bed, accumulated at river deltas, which were displaced by the shock and unleashed the waves as they moved, the study says. Waves were reported west, north and south of the epicentre, which was within a few kilometres of the surface on the Enriquillo-Plaintain Garden fault, on the boundaries of two microplates in the Caribbean. Such 'slide-generated' tsunami are rare, but their risk is underestimated, according to the paper, published online in the journal Nature Geoscience. 'Even modest, predominantly strike-slip earthquakes can cause potentially catastrophic slide-generated tsunami,' it says. A strike-slip earthquake occurs when one side of the fault moves along horizontally and in parallel to the other side of the fault, rather than down or up. Vertical displacement, especially of the seabed, is best known for creating tsunamis. The study was led by a team led by Matthew Hornbach of the University of Texas at Austin. The January 12 quake was in tectonic terms a surprisingly complex affair, according to new research. Two-thirds of the movement was strike-slip, and a third was a thrust, or upward, movement. The quake inflicted huge damage to the capital, Port-au-Prince, injuring 300,000 people and leaving 1.5 million homeless. -- AFP