GPS data collected in the Dominican Republic from 1994 to 2001 show that oblique convergence between the North American and Caribbean plates is parti-tioned between 5.2+-2 mm/yr of dip-slip reverse motion on the North Hispaniola thrust (approximately N-S), and 12.8+-2.5 mm/yr and 9.0+-9.0 mm/yr of approximately E-W left-lateral strike-slip motion on the Septentrional and Enriquillo faults (95% confidence). The agreement between GPS and paleoseimological slip rates on the Septentrional fault, together with the 770-960 years since the last major earthquake and the 800-1200 years maximum repeat time of major earthquakes, may indicate that the Septentrional fault is currently in the late phase of its rupture cycle. A fully locked fault accumulating elastic strain at 13 mm/yr implies a current slip deficit of 9.5 m, equivalent to a Mw=7.6-7.8 earthquake if it was entirely released today in a single event. This makes the Septentrional fault a source of high seismic potential in a densely populated and rapidly developing area of the Dominican Republic.

Top: GPS-derived velocities in the Dominican Republic and western Puerto Rico with respect to the North American Plate. The arrow length is proportional to the displacement rate, indicated in mm/yr next to the site code name. The ellipses represent 95% confidence intervals. Most sites in the Dominican Republic have only been observed twice two years apart in 1999 and 2001. Note the more northerly vectors along the north coast, reflecting northward thrusting of the Septentrional sliver at the North Hispaniola fault zone. Bottom inset shows the study area. Right: Contour plots of the chi2 statistic. The dashed line show the limit of the 95% confidence area. A. Chi2 statistic for the [Enriquillo strike-slip, Septentrional strike-slip] tests. B. Chi2 statistic for the [North Hispaniola strike-slip, North Hispaniola dip-slip] tests.

See also:
Calais, E., Y. Mazabraud, B. Mercier de Lépinay, P. Mann, P.E. Jansma, and G.S. Mattioli, Oblique collision and strain partitioning from GPS measurements in the northeastern Caribbean, Geophys. Res. Letters , in press, 2002.