Seismotectonics of southern Haiti: A new faulting model for the 12 January 2010M7.0 earthquake

Abstract

The prevailing consensus is that the 2010 Mw7.0 Haiti earthquake left the Enriquillo‐Plantain Garden strike‐slip fault (EPGF) unruptured but broke unmapped blind north dipping thrusts. Using high‐resolution topography, aerial images, bathymetry, and geology, we identified previously unrecognized south dipping NW‐SE striking active thrusts in southern Haiti. One of them, Lamentin thrust, cuts across the crowded city of Carrefour, extends offshore into Port‐au‐Prince Bay, and connects at depth with the EPGF. We propose that both faults broke in 2010. The rupture likely initiated on the thrust and propagated further along the EPGF due to unclamping. This scenario is consistent with geodetic, seismological, and field data. The 2010 earthquake increased the stress toward failure on the unruptured segments of the EPGF and on neighboring thrusts, significantly increasing the seismic hazard in the Port‐au‐Prince urban area. The numerous active thrusts recognized in that area must be considered for future evaluation of the seismic hazard.

Late Holocene Structural Style and Seismicity of Highly Transpressional Faults in Southern Haiti

“…However, postearthquake geologic reconnaissance revealed no fault‐related, surface ground breaks along the proposed onland areas of EPGFZ in the epicentral region of the earthquake (Koehler & Mann, ; Prentice et al, ; Rathje et al, ). A more recent study by Saint Fleur et al () proposed previously, unrecognized, 2010 coseismic groundbreaks along the obliquely striking Lamentin thrust 11 km east of the epicentral area near the city of Port‐au‐Prince (Figure a).…”

“…The elongate belt of transpressional deformation associated with en echelon thrusts occupies a topographically low, densely populated Cul‐de‐Sac basin underlain by poorly consolidated, clastic sedimentary rocks ranging in age from Miocene to recent (Bachhuber et al, 2010; Mann et al, ; Rathje et al, , ; Saint Fleur et al, ; Terrier et al, ). In easternmost Haiti, this belt is overlain by the shallow (33 m deep), 138 km 2 , brackish Lake Azuey near the border separating Haiti from the Dominican Republic (Piasecki et al, ; Wright et al, ).…”

“…On 12 January 2010, a M w 7.0 earthquake struck the densely populated, greater Port‐au‐Prince region of south central Haiti and caused widespread destruction with over 230,000 fatalities and an estimated 10 billion dollars in damage (Bilham, ; Kocel et al, ; Paultre et al, ; Prentice et al, ; Figure ). Multidisciplinary, geological, and geophysical studies within the 2010 epicentral area of south central Haiti include the following: (1) measurements and fault modeling of coseismic, coral reef uplift along a 50‐km‐long area of coastline in the epicentral region (Hayes et al, ); (2) coseismic, vertical ground motion from radar interferometry (Hashimoto et al, ); (3) high‐resolution, surface fault trace mapping using Light Detection And Ranging and targeted field studies (Cowgill et al, ); (4) Global Positioning System (GPS) and 2010 aftershock‐based studies and modeling of pre‐, syn‐, and post‐2010 earthquake crustal motions (Calais et al, ; Douilly et al, , ; Nettles & Hjörleifsdóttir, ; Symithe et al, ); (5) ground‐based studies of Holocene scarps including coseismic ground fractures and late Quaternary scarps of the Enriquillo‐Plantain Garden fault zone (EPGFZ) that remained unaffected by 2010 fault breaks (Koehler & Mann, ; Prentice et al, ; Rathje et al, ; Saint Fleur et al, ); (6) ground‐based, near‐surface, geophysical surveys of buried faults activated during the 2010 earthquake (Kocel et al, ); (7) near‐coast surveys of submarine extensions of faults active in 2010 (Hornbach et al, ; Mercier de Lépinay et al, ); and (8) deepwater, marine surveys and coring to determine the recurrence interval of major earthquakes based on anomalous sedimentary deposits related to shaking and increased erosion (McHugh et al, ).…”

“…The study by Saint Fleur et al () indicates that the folding and thrusting of 10‐ to 15‐km‐wide belt of Miocene to Quaternary sedimentary rocks were generated by transpression along the EPGFZ. In addition, Mann et al (), Grindlay et al (), and Kroehler et al () suggest a strong, southwestward, back thrusting of the southern Hispaniola in Haiti and Dominican Republic to the southwest onto the Caribbean plate (Figures b and c).…”

3‐D velocity structure in southern Haiti from local earthquake tomography

“…This raises possibility that the Trois Baies and the Léogâne faults are representative of previously unrecognized active faults. Recently, Saint Fleur et al [] mapped a south dipping thrust fault that they referred to as the Lamentin fault. This fault runs offshore at the Canal‐du‐Sud and continues onshore to connect to the EPGF.…”