An as yet undescribed fault that runs close to the town of Leogane was implicated in the earthquake that wreaked havoc in Haiti in January 2010, suggests a study published online this week in Nature Geoscience. The movement caused the surface to bulge, but not to rupture. The paper is part of Nature Geoscience’s special issue on the Haiti earthquake.

Eric Calais and colleagues analysed data on ground motion from GPS systems and radar interferometry. From the observed patterns, they conclude that a previously unknown fault must have been active in the 12 January 2010 event.

The researchers conclude that the Haitian earthquake did not come entirely unexpectedly, given the seismic activity in the region. However, despite remaining uncertainties the detailed mechanics of the event will require revisions to conventional ideas of the fault system in the region.