Present motion and deformation of the Caribbean plate: Constraints from new GPS geodetic measurements from honduras and Nicaragua

Velocities from six continuous and 14 campaign sites within the boundaries of the Caribbean plate, including eight new sites from previously unsampled areas of Honduras and Nicaragua at the western edge of the Caribbean plate, are described and tested for their consistency with Caribbean-North America plate motion and a rigid Caribbean plate model. Sites in central Honduras and Guatemala move 3-8 mm yr -1 westward with respect to the Caribbean plate interior, consistent with distributed east-to-west extension in Guatemala and the western two-thirds of Honduras. A site in southern Jamaica moves 8 ± 1 mm yr -1 westward relative to the Caribbean plate interior, indicating that most or all of Jamaica is unsuitable for estimating Caribbean plate motion. Two sites in southern Hispaniola also exhibit anomalous motions relative to the plate interior, consistent with a tectonic bias at those sites. An inversion of the velocities for 15 sites nominally located in the plate interior yields a well-constrained Caribbean plate angular velocity vector that predicts motion similar to previously published models. Data bootstrapping indicates that the solution is robust to better than 1 mm yr -1 with respect to both the site velocities that are used to estimate the plate angular velocity and the site velocity uncertainties. That velocities at seven of eight GPS sites in eastern Honduras and Nicaragua are consistent with the motions of sites elsewhere in the plate interior indicates that much or all of eastern Honduras and Nicaragua move with the plate interior within the 1-2 mm yr -1 resolution of our data. It further suggests that the morphologically prominent, but aseismic Guayape fault of eastern Honduras is inactive. Tests for possible east-to-west deformation across the Beata Ridge and Lower Nicaraguan Rise in the plate interior establish a 95% upper bound of ̃2 mm yr -1 for any deformation across the two features, significantly slower than a published estimate of 9.0 ± 1.5 mm yr -1 . during the past 23 Ma for deformation across the Beata Ridge. © 2007 The Geological Society of America. All rights reserved.