Oblique collision in the northeastern Caribbean from GPS measurements and geological observations

Previous Caribbean GPS studies have shown that the rigid interior of the Caribbean plate is moving east-northeastward (070degrees) at a rate of 18-20+/-3 mm/yr relative to North America. This direction implies maximum oblique convergence between the island of Hispaniola on the Caribbean plate and the 22-27-km-thick crust of the Bahama carbonate platform on the adjacent North America plate. We present a tectonic interpretation of a 15-site GPS network which spans the Hispaniola-Bahama oblique collision zone and includes stable plate interior sites on both the North America and Caribbean plates. Measurements span the time period of 1994-1999. In a North America reference frame, GPS velocities in Puerto Rico, St. Croix, and the Lesser Antilles indicate that these areas move as a single block in an east-northeast direction (070degrees) at a rate of 19-20 mm/yr consistent with the movement of the rigid interior of the Caribbean plate. GPS velocities at six sites in central and eastern Hispaniola (Dominican Republic) show drastically different behavior with more eastwardly strikes (080degrees) and much slower rates (4-17 mm/yr) than areas of the stable Caribbean plate. The boundary between the relatively slower-moving Hispaniola collisional zone and the relatively faster-moving, uncollided Puerto Rico-Virgin Islands area is the Mona Passage where late Neogene rifting occurs in a broad zone. Elastic modeling favors strain partitioning with oblique slip on the outer, low-angle submarine thrust faults (North Hispaniola, Muertos) and strike slip on the inner, subvertical subaerial, strike-slip faults (Septentrional, Enriquillo).