On January 12, 2010, a M_w7 earthquake struck the Port-au-Prince region of Haiti, killing an estimated 230,000 people, leaving more than 1.5 million homeless, costing 120% of the country’s GDP, and destroying most governmental, technical, and educational infrastructure throughout this region of 3 million people. Despite warnings from the geoscience community that Haiti was at high risk for an earthquake, the country found itself unprepared. With historical seismicity indicating that this earthquake may be the beginning of a new cycle of large events, we have conducted a number observational and modeling experiments to better understand what transpired during the earthquake, determine where seismic hazards are greatest in the years to come, and to prepare the people of Haiti for this eventuality.

Intellectual Merit

    To better understand what transpired during the 2010 Haiti earthquake we solved for the geometry and slip distribution using a combination of relocated aftershocks, and GPS, coastal uplift, and InSAR co-seismic displacements. Our preferred model involves two main slip patches on adjacent segments of the previously unknown Léogâne fault, with a combination of reverse and strike-slip motion. We also simulated the propagation of the rupture and were able to show that this two-segment, planar fault geometry can successfully replicate the seismically observed rupture propagating from east to west and the geodetically inferred finite ground displacement. We then used these models to calculate coseismic Coulomb stress changes (how stress changes inhibit or promote failure of nearby faults) to show that (1) the aftershock cluster found on the Trois Baies reverse fault is a direct result of slip on the Léogâne fault, and (2) that coseismic slip. increased Coulomb stress on various sections of the Enriquillo fault, potentially advanced the time of occurrence of the next earthquake on the major fault system in southern Haiti. To further understand seismic hazards in the region, we assembled an up-to-date GPS velocity field for the Caribbean plate which we used to quantify the kinematics of active deformation. We found low coupling (the degree to which faults resist slip) and a corresponding low seismic hazard along the Lesser Antilles subduction interface, but high coupling and seismic hazard associated with the strike-slip plate boundary along the northern and southern margins of the Caribbean plate. Furthermore, we used the improved GPS data set to show that active strain accumulation in Port-au-Prince region suggests that triggering of a fault in that region has the potential to generate ground motion twice as large as what might expect from an earthquake on the Enriquillo Fault. Finally, we performed a joint inversion for a 3-D P and S wave velocity structure that reveals strong lateral variations both onshore and offshore of Haiti’s southern peninsula, including a sharp low-velocity zone running along the Petit-Goâve-Jacmel fault (PGJF). This may indicate another major active fault in the region.

Broader Impacts

    Broader impacts of this project included improving our understanding of the hazards associated with earthquakes in Haiti following the 2010 event. Our work helped to define the likelihood that other large earthquakes may be impending along that fault system. We also continued to train our Haitian collaborators in the use of modern space geodetic techniques, with the hope that they can continue to monitor and learn to access their own seismic hazards. To this end, to help initiate the capacity building effort in geosciences that is so much needed in Haiti, we used this grant to help two Haitian students earn MS and PhD degrees at Purdue, enabling them to develop expertise in earthquake related observational and modeling techniques. One of these students is now a professor in Haiti, while the other is continuing his studies as a postdoctoral scholar in the US. While conducting our GPS work in Haiti, we also visit a number of high schools in the towns we pass through to discuss the tectonics and earthquake hazards. We also conducted several live interviews on radio and television during our visit.

Last Modified: 02/23/2017
Modified by: Andrew Freed