Transpressional rupture of an unmapped fault during the 2010 Haiti earthquake
Freed, Andrew M.
Mattioli, Glen S.
Jansma, Pamela E.
Dixon, Timothy H.
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
Environmental Science and Engineering Program
Crustal Deformation and InSAR Group
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AbstractOn 12 January 2010, a Mw7.0 earthquake struck the Port-au-Prince region of Haiti. The disaster killed more than 200,000 people and caused an estimated $8 billion in damages, about 100% of the country?s gross domestic product. The earthquake was initially thought to have ruptured the Enriquillog-Plantain Garden fault of the southern peninsula of Haiti, which is one of two main strike-slip faults inferred to accommodate the 2cmyr -1 relative motion between the Caribbean and North American plates. Here we use global positioning system and radar interferometry measurements of ground motion to show that the earthquake involved a combination of horizontal and contractional slip, causing transpressional motion. This result is consistent with the long-term pattern of strain accumulation in Hispaniola. The unexpected contractional deformation caused by the earthquake and by the pattern of strain accumulation indicates present activity on faults other than the Enriquillog-Plantain Garden fault. We show that the earthquake instead ruptured an unmapped north-dipping fault, called the Léogâne fault. The Léogâne fault lies subparallel tog-but is different fromg-the Enriquillog-Plantain Garden fault. We suggest that the 2010 earthquake may have activated the southernmost front of the Haitian fold-and-thrust belt as it abuts against the Enriquillog-Plantain Garden fault. As the Enriquillog-Plantain Garden fault did not release any significant accumulated elastic strain, it remains a significant seismic threat for Haiti and for Port-au-Prince in particular. © 2010 Macmillan Publishers Limited. All rights reserved.
SponsorsThe results presented here owe to many collaborators, contributors and friends in Haiti, in particular the National System for Disaster Risk Reduction (A. Nazaire) and the Civil Protection Agency (A. Jean-Baptiste), the Bureau of Mines and Energy (D. Anglade) and the National Center for Geospatial Information (G. Porcena and B. Piard). M. Jeannite and F. S. Preux from the Bureau of Mines and Energy carried out the bulk of the GPS fieldwork in Haiti. We thank D. Anglade (General Director) and S. L. Mildor (Director for Geology) from the Bureau of Mines and Energy for their constant support. The post-earthquake GPS survey benefited from field support from D. Sarah Stamps and E. Chaussard. UNAVCO provided outstanding support to the field operations in Haiti. A. Holsteinson (Holasa Inc.) carried out the 2009 and 2010 GPS measurements in the Dominican Republic. The ALOS data were provided by GEO's Geohazard Supersites and are copyrighted by the Ministry of Economy, Trade and Industry of Japan and Japan Aerospace Exploration Agency. This research was supported by grants from the National Science Foundation (grants no 0409487 and RAPID no 1024990 to E.C., no 0408978 to G.M./P.J.) and the National Disaster Risk Management System Development Program UNDP Haiti.