12 Jan 2010 at 04:53:10 PM local time
location 18.457 deg N, 72.533 deg W, Mw =7.0
The earthquake occurred on an east-west, strike-slip fault. Rupture was roughly 65 km long with mean slip of 1.8 m. According to preliminary models the rupture propagated bilaterally with most of the slip over in the first 15 s, and with maximum slip near the epicenter exceeding 4 m.
The epicenter was roughly 8 km deep and the surface fault will almost certainly have ruptured throughout the pronounced valley that marks its passage through the mountains south of Port au Prince. Aftershocks delineate the east west extent of the rupture.
The urban agglomeration of Port au Prince has expanded rapidly in the past decade and now exeeds 2 million. The death toll is currently estimated at 50,000 (15 January 2010). Max Wyss of WAPMERR issued a forecast up to 60,000 fatalities within 30 minutes of the mainshock based on population density, earthquake magnitude, generalized attenuation, and building fragility.
A recent article discussing the seismic future of cities may be downloaded here. The 12 January earthquake was a relatively modest earthquake, but its large death-toll is caused by its proximity to a poorly constructed city.
A book by Susan Hough and Roger Bilham discusses the increasing problem of urban earthquakes.