Microplate behavior in the northeastern Caribbean plate boundary zone as constrained by Global Positioning System geodesy

The Puerto Rico-Virgin Islands (PRVI) microplate lies within the broad northern Caribbean plate boundary zone (NCPBZ). Seismicity and marine geophysical data have been interpreted to indicate active offshore structures which define the boundaries of PRVI microplate. Data from the GPS geodetic network in PRVI since 1994 constrain the motion of PRVI with respect to stable North American (NA) (16.9 ± 1.1 mm/yr towards N68°E ± 3°), and Caribbean plates (2.3 ± 1.4 mm/yr towards N78°W ± 33°) at the 95% confidence level. In a fixed NA reference frame, the velocities derived by the GPS suggest PRVI is translating as a rigid block within the NCPBZ towards the east-northeast. 80% of the motion between North American-Caribbean plates is accommodated at the northern boundary of the NCPBZ. Extension between Hispaniola and PRVI is occurring along the Mona Canyon in the west. The southern boundary of the NCPBZ shows a slow left-lateral motion with convergence, whereas the eastern boundary shows no significant motion.