Assessing the Rigidity of the Puerto-Rico Northern Virgin Islands Microplate: Results from GPS Geodesy in the British Virgin Islands Abstract

abstract

  • Recent studies provide evidence of three microplates defined by the Puerto Rico trench to the north and the Muertos trough to the south in the boundary zone between the North American and Caribbean plates in the northeastern Caribbean. From west to east, these are the Gonave, Hispaniola, and Puerto-Rico Northern Virgin Islands (PRVI) microplates. The eastern and western boundaries of the Gonave and Hispaniola microplates, and the western boundary of the PRVI microplate have been defined in previous studies. However, the easternmost terminus of PRVI is undetermined, but suspected to lie either within or at the eastern terminus of the British Virgin Islands (BVI). Previously reported geodetic data indicates east-west extension across Puerto Rico and between eastern Puerto Rico and Virgin Gorda in the BVI. Our 2005 campaign focused on defining the easternmost terminus of the PRVI and testing the extensional hypothesis by collecting surface motion data using Global Positioning System (GPS) geodesy. We collected data at sites on Tortola and Anegada in the BVI and concluded that the GPS-derived velocities of Tortola and Anegada with respect to the Caribbean are 5.71 + or - 5.5 mm/yr to the NNW (one sigma)and 3.12 + or - 2.7 mm/yr to the WNW (one sigma) respectively. These velocities are similar to those of eastern Puerto Rico. No motion relative to the Caribbean for Tortola and Anegada also is a possibility within error. If the GPS-derived velocities of Tortola and Anegada are 3-5 mm/yr, little to no east-west extension occurs between the BVI and eastern Puerto Rico, implying that PRVI is rigid at the mm/yr level and that the eastern most terminus coincides with the eastern end of the BVI near Virgin Gorda.

authors

publication date

  • 2006

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