Résumé
Along the northern strike-slip boundary of the Caribbean plate, strain is partitioned and accommodated by the relative motion of several microplates. Among these microplates, the Gonâve microplate is bounded by two major strike-slip fault systems: the Enriquillo Plantain Garden Fault Zone (EPGFZ) to the south and the Septentrional-Oriente Fault Zone (SOFZ) to the north, with the Cayman Trough and the Haitian Fold and Thrust belt defining its western and eastern limits, respectively. On 12 January 2010, a devastating Mw 7.0 earthquake struck along the EPGFZ, cross-cuts the southern peninsula of Haïti and the southern Gulf of Gonave. This earthquake, occurring on an uncharacterized fault segment, was both destructive and unexpected. Since then, geophysical and geological investigations have been performed to improve understanding of the fault geometries, kinematics and strain rates in the region. This study used multibeam bathymetry and reflection seismic data from various oceanographic campaigns in the Gulf of Gonave to highlight the spatial and temporal evolution of these structures. Data analysis revealed NE-SW trending tilted blocks belonging to the continental margin of the East Cayman Trough. Several of these blocks are bounded by low-angle normal faults, suggesting intense stretching. The various identified seismic horizons allow us to date the top of the syn-rift units in the Gulf of Gonave and confirm that rifting occurred between 49 and 56 Ma. Consequently, the eastern Cayman margin extends from northern Jamaica in the west to at least the eastern Gulf of Gonave, covering a typical continental margin distance of 450 km with a thinning rate of 2.7. Our study reveals that all extensional structures were later inverted by NE-SW-oriented compression, aligned with the trend of the tilted blocks in the Gulf of Gonâve. Shortening rates calculated from the Gulf of Gonave seismic profiles are compared with those obtained from onshore geological data and GPS block models. Notably, the shortening calculated in the Gulf of Gonave appears to be lower than the GPS-derived convergence rates of 6-7 mm/yr, suggesting a possible increase in deformation rates over time. Additionally, short-term deformation occurs on a reverse fault system in the southern Gulf of Gonâve. Based on the available data and the results of our study, we propose a novel model for the spatiotemporal evolution of tectonic structures extending from the northern Jamaican margin in the west to the Haitian fold-and-thrust belt in the east.