Crustal deformation in the northeastern Caribbean

HR: 0830h
AN: T11B-02 INVITED
TI: Crustal deformation in the northeastern Caribbean from GPS measurements
AU: * Calais, E
EM: Eric.Calais@unice.fr
AF: CNRS, GＰsciences Azur, Valbonne, France
AU: Mann, P
AF: Institute for Geophysics, Univ. of Austin, United States
AU: Ruegg, J
AF: Institut de Physique du Globe, 4 Pl. Jussieu, Paris, France
AU: DeMets, C
AF: Dpt. of Geology and Geophysics, University of Wisconsin, Madison, United States
AU: Dixon, T
AF: Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, United States
AU: Jansma, P
AF: Dpt. of Geology, University of Puerto Rico, Mayaguez, United States
AU: Mattioli, G
AF: Dpt. of Geology, University of Puerto Rico, Mayaguez, United States
AU: Bilham, R
AF: Department of Geological Sciences, University of Colorado, United States

AB: We have combined GPS data sets collected by collaborating US and French institutions in the northeastern Caribbean in order to address regional-scale crustal deformation. The data set includes 15 sites in the Dominican Republic, Puerto Rico, and the Virgin Islands (US-French CANAPE project), 4 sites in Martinique and Guadeloupe in the Lesser Antilles (Institut de Physique du Globe de Paris), and 1 site on Aves island (University of Colorado). In addition, we benefit from GPS data at the permanent IGS sites of St. Croix and Barbados, and at sites in Puerto Rico (University of Puerto Rico Mayaguez). The GPS-derived velocities show that the Puerto Rico-Virgin Islands-Lesser Antilles-Aves area is currently behaving as a rigid block, part of the stable Caribbean plate, moving in an east-northeast direction (070) at a rate of 19-20 mm/yr relative to North America. In Hispaniola, velocities significantly deviate from a rigid Caribbean plate model, with more easterly strikes (N80E) and slower rates (4-17 mm/yr) relative to North America. We show that velocities in Hispaniola are compatible with a model of elastic strain accumulation on 4 major fault zones, currently locked to a depth of 15 km (North Hispaniola, Septentrional, Enriquillo fault, Muertos). GPS-derived velocities are consistent with earthquake slip vectors and predict oblique thrusting at the North Hispaniola fault and subduction at the Puerto Rico trench. GPS-derived velocities require a large amount of thrust motion on the NHF (10 mm/yr or more). This result is consistent with a model of oblique collision between Hispaniola and the Bahama platform, where a significant amount of the Caribbean/North America motion is accomodated on a relatively shallow dipping thrust fault along the collisional interface. GPS results indicate that Hispaniola is currently accumulating 12 mm/yr of shorterning over 200 km (0.05x10-6 yr-1), but that Puerto Rico-Virgin Island-Aves are deforming at very low rates (0.005x10-6 yr-1 or less). We discuss the implications of this result in terms of the complex extensional deformation of the Mona Passage between Hispaniola and Puerto Rico and in terms of the variations in regional seismic hazard.

DE: 8105 Continental margins and sedimentary basins
DE: 1206 Crustal movements--interplate (8155)
SC: T
MN: Fall Meeting 2000