via news.bbc.co.uk
The 7.0-magnitude earthquake that rocked Haiti on Tuesday occurred along a strike-slip fault, the same type as California's San Andreas fault. Pressure had probably been building for centuries.
The Washington Post shares an infographic
The earthquake that devastated the Haitian capital of Port-au-Prince on 13 January also affected many outlying towns - the extent of which is only being discovered days after the disaster.