Global Positioning System (GPS) Determination of Motions, Neotectonics, and Seismic Risk in Trinidad

A. B. Rodriguez¹, J. C. Weber¹, and G. M. Schmalzle^2
1Department of Geology, Grand Valley State University, Allendale, Michigan, USA
²RSMAS-MGG, University of Miami, Miami, Florida, USA

Trinidad is located in the actively deforming Caribbean-South American (Ca-SA) plate boundary zone and is one of the region’s major producers of oil and gas. Geodetic GPS work over the past decade has accurately determined that the Caribbean plate moves approximately ~20 mm/yr eastward relative to the South American plate. A low-precision triangulation-to-GPS comparison and paleoseismology showed that ~12 mm/yr of active strike-slip faulting is probably occurring on the Central Range Fault (CRF). The lack of recent seismic activity on the CRF may indicate that it is elastically locked, if so, it could pose a significant seismic risk for the island’s petroleum infrastructure and population. We study Trinidad’s neotectonics using GPS data from 19 high-stability sites that were built and measured in 2005, then measured again in 2007. We processed the data using GIPSY/OASIS II (Release 5.0) software at the University of Miami RSMAS Geodesy Lab. We find that in a South American reference frame sites north of the CRF are on the Caribbean plate and move at about 20 (±1-5) mm/yr; sites south of the CRF are stationary (±1-8 mm/yr) and on the South American plate. Our results support the hypotheses that the CRF is the principal active strike-slip fault in Trinidad (i.e., is the current Ca-SA plate boundary). We are fitting locked fault (elastic dislocation half-space) models to these data that will allow us to look more closely at the mechanical behavior of the CRF, to establish its slip rate, and whether it is locked or creeping.

AAPG Search and Discover Article #90087 © 2008 AAPG/SEG Student Expo, Houston, Texas