Geologia Del Caribe

Quantifying crustal deformation and accumulation of strains along PRVI microplate boundaries

David J. Rodríguez Castro
GEOL 4049: Undergraduate Research I
University of Puerto Rico, Mayagüez
Department of Geology

Content

Abstract
Over 93 years ago a big earthquake affects western part of Puerto Rico, the impact caused by this earthquake was hundreds of deaths and economic lossesprimarily in the agriculture of the west coast. We've spent much time and thought that major earthquake and catastrophic tsunami occurred, but today with are in a seriously risk maybe next earthquake could be more powerful. This research opens new way to been able to verify the level of deformation of the crust that causes seismic activity around our region. To accomplish this analysis we shouldwork with GPS data that gave us position relative to the reference frame and geographic location, satellite orbits for exact precision and we can get displacement data from the 15 GPS stations over the region. These GPS stations are located along the entire region of Puerto Rico and the Virgin islands. The GPS data are processed to get the exact displacements that would be detected over past years(dx/dt, velocities) and modeled in lithospheric blocks to obtain then a clear visualization of the accumulation of stresses and strains occurring in the boundaries of Puerto Rico and Virgin Islands microplate to get know the potential risk of a major earthquake in our region. The preliminary results shows areas of deformation along some areas around the Puerto Rico and Virgin island microplate,making this technique effective to identify places that occur crustal deformation around the region.
Key Words:
* Crustal Deformation

* Lithospheric Blocks

* DEFNODE

* Angular velocities

* Puerto Rico and Virgin Island Microplate

Introduction
A very complex tectonic picture surrounds Virgin Islands and Puerto Rico(figure 1). Multiple faults and trenches thathave not been studied in detail surround both islands( Mann,1999). Two major plates govern convergence zones that develop in this region: The plate of North America and the Caribbean plate. Today the Caribbean Plate are moving 18-20 mm / yr. in direction N70 ° E with respect to the North American plate (Mann et al, 2002). This movement caused by the subduction of the Caribbean plate is up and NorthAmerica plate that goes under, contribute to the formation of the volcanic arc of the Greater Antilles. The subduction process contributes to the formation of the Puerto Rico Trench which produces a very oblique (10 °) and is accompanied by the development of systems of tears faults or horizontal displacement faults of hundreds of kilometers along the fore arc (Brink et al, 2004) and also thisgenerated a very active seismic activity by the energy released over the region. South of the islands of the eastern Caribbean, where under normal conditions should develop an area of ​​Trans arc, but it is not occur, in its place would be found “The Muertos Trench” which is generating the subduction of the oceanic crust of the Basin Venezuela to the northeast beneath the island arc resulting in theaccretionary prism or "Los Muertos Deformed Belt" (Ladd et al, 1977, Byrne et al, 1985, Manson & Scanlon, 1991; Carbo et al, 2005). The place where the level of subduction that is most active located southeast of the Hispaniola around 3 mm /yr (Calais et al 2002) and diminishes or disappears to the east (Manson & Scanlon, 1991; Carbó et al, 2005). However, "The Muertos Trench" located justsoutheast of the Hispaniola island, has some deviation toward the northwest, where it disappears, but according to (Duval et al 1982) suggest that there is continuity with fault zones on the island of the Hispaniola, for example, "Graden Plaintain Enriquillo fault."
Furthermore, convergence processes are replaced by tears faults and sinextral faults that are oriented toward the northeast...