New GPS Constrains on Crustal Deformation within the Puerto Rico-Virgin Islands Microplate

Abstract:

Over twenty years of Global Positioning System (GPS) observations along the northeastern region of the Caribbean plate boundary zone have been used to evaluate crustal deformation in the Puerto Rico and Virgin Islands (PRVI) microplate, which generally translates westward relative to the Caribbean plate. New data from continuous GPS stations (cGPS) and re-occupied campaign GPS stations (eGPS) obtained between 2014 and 2015 allowed us to update the velocity field of the PRVI GPS Network and redefine the existing plate kinematics model of the PRVI microplate from previous measurements (Jansma et al., 2000; Jansma & Mattioli, 2005). Geodetic datasets for this epoch were processed with GIPSY/OASIS II (v.6.2) using an absolute point positioning strategy with final, precise orbits and clocks from JPL (IGS08). Results of sites velocity in the PRVI block are presented with respect to North America and Caribbean reference frames in ITRF08. The horizontal velocity components were used to calculate baseline lengths changes between selected GPS stations that span on-land faults and microplate boundaries, thus allowing quantification of internal deformation within the PRVI block. This enables us to locate zones of active deformation and faulting in order to understand how the relative motion between geological structures is accommodated. Our updated velocity field constrains intraplate deformation to 1-3 mm/yr across the PRVI microplate and active extension of 1-2 mm/yr in the Anegada passage eastern boundary. In addition, counterclockwise rotation has been observed and may be related to the deformation in southwestern Puerto Rico continuing offshore to the Muertos Trough along PRVI’s southern boundary. Despite the PRVI microplate slow motion and small deformation, increasing velocities from east to west coincides with the most active microseismic zone and ongoing deformation in southwestern Puerto Rico suggesting independent motion along this segment of the PRVI block.