Unraveling Complexity of Haiti Quake Reveals Hidden Faults and Future Hazards

The January 2010 M7.0 earthquake that devastated Haiti’s economy and caused over 200,000 casualties also resulted in significant uplift of the ground surface along Haiti’s coastline, and involved slip on multiple faults, according to a study published online in Nature Geoscience.

Because the earthquake did not involve slip near the surface of the Earth, the study suggests that it did not release all of the strain that has built up on faults in the area over the past two centuries, and so future surface rupturing earthquakes in this region are likely.

The paper also suggests that similar events may be hidden from the prehistoric earthquake record both in Haiti and in other similar tectonic settings such as the San Andreas fault in California.

Gavin Hayes, a U.S. Geological Survey geophysicist, along with colleagues from USGS, California Institute of Technology, NASA’s Jet Propulsion Laboratory (JPL), and the University of Texas at Austin, used a combination of seismological observations, geologic field data and satellite geodetic measurements to analyze the earthquake source. Initially the Haiti earthquake was thought to be the consequence of movement along a single fault, which accommodates the motion between the Caribbean and North American plates.

By modeling the patterns of surface deformation, the team was able to assess which fault was responsible. Their results showed that the earthquake may not have been caused by the simple rupture of a single fault, but instead may have involved a complex series of faults.

The pattern of surface deformation was dominated by movement on a previously unknown, subsurface thrust fault, named the Léogâne fault, which did not rupture the surface.

Hayes, a post-doctoral researcher, is contracted to work for the USGS by Synergetics, Inc.

This is one of several papers to be published this month in a special issue of  Nature Geoscience on the Haiti earthquake.

*Source: U.S. Geological Survey (USGS)

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