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.

The Earth's tectonic plates courtesy of the U.S. Geological Survey

Collission or convergent boundaries. Where plates collide. Plate edges may be either oceanic crust or continental crust. So when plates collide, we have only three possibilities: oceanic-oceanic, oceanic-continental, or continental-continental collisions. If oceanic crust collide with continental crust, the denser oceanic crust is subducted under the less dense continental crust (as at the Ring of Fire). If continental crust collide with continental crust they push each other up in a mountain range (like the Himalayas).