HR: 1330h
AN: G43B-03    [Abstracts]
TI: Strain Accumulation Models in the Lesser Antilles Using GPS Geodesy
AU: * Fitzgibbon, K M
EM: kfitzgi@uark.edu
AF: Department of Geosciences, University of Arkansas, 113 Ozark Hall, Fayetteville, AR 72701 United States
AU: Turner, H L
EM: hturner@uark.edu
AF: Department of Geosciences, University of Arkansas, 113 Ozark Hall, Fayetteville, AR 72701 United States
AU: Mattioli, G S
EM: mattioli@uark.edu
AF: Department of Geosciences, University of Arkansas, 113 Ozark Hall, Fayetteville, AR 72701 United States
AU: Jansma, P E
EM: pjansma@uark.edu
AF: Department of Geosciences, University of Arkansas, 113 Ozark Hall, Fayetteville, AR 72701 United States
AB: In the northeastern Caribbean, convergence along the Caribbean - North American plate boundary is oblique and relatively slow. Subduction is near normal in the southern Lesser Antilles but becomes more oblique in the north, particularly near Cuba. Estimates of locking on the plate interface are controversial and vary from zero to 50% in the north but are generally agreed to be zero in the south. Compounding the difficulties in determining strain accumulation from locking, movement of the Caribbean plate is not well constrained, and errors in the Caribbean reference frame are large compared with observed site velocities. To constrain locking on the plate interface, GPS measurements have been taken since 1994 at stations installed on islands of the Lesser Antilles. In July and August of 2004, observations were made on the islands of Anguilla, St. Maarten, St. Kitts and Nevis in the northern Lesser Antilles at nine sites that were established and initially occupied in 2000 - 2002. More than 2.5 days of continuous observation using dual-frequency code-phase receivers and choke ring antennae were obtained at each site. Because stations are small and far apart and the locations less than ideal for needed measurements, observations from the 2000 - 2004 campaigns were compared with predictions from simple elastic half-space models developed using DISL. Observed velocities vary significantly from the models in both magnitude and direction. Preliminary models predict a very small signal from strain accumulation related to subduction (on the order of less than 2 mm/a to the southwest). Observed velocities have larger magnitudes, however, which may indicate contamination from local tectonics, slope instabilities, and volcanic deformation. Velocity orientations show an overall consistency with locking on the plate interface. Removing the effects of strain accumulation from observed velocities should help constrain local tectonic effects and allow us to test models of upper plate deformation and Caribbean plate rigidity.
DE: 1206 Crustal movements--interplate (8155)
SC: Geodesy [G]
MN: 2005 Joint Assembly