HR: 0800h
AN: T11B-0393    [Abstracts]
TI: Effects of a Possible Northern Lesser Antilles Forearc Block on Northeastern Caribbean kinematics and hazards
AU: * López, A M
EM: alberto@earth.northwestern.edu
AF: Northwestern University, 1850 Campus Drive Locy Hall, Evanston, IL 60208 United States
AU: Stein, S
EM: seth@earth.northwestern.edu
AF: Northwestern University, 1850 Campus Drive Locy Hall, Evanston, IL 60208 United States
AB: An intriguing question concerning the Northeastern Caribbean is the occurrence of a systematic discrepancy between slip vectors of thrust fault earthquakes at the Lesser Antilles trench (LAT) and the predicted direction of convergence between North American (NA) and Caribbean (CA) plates. Although it had seemed possible that the discrepancy resulted from the fact that neither direction was well constrained, it persists using a larger set of slip vectors and a Caribbean-North America Euler vector derived using GPS data from sites within the presumably stable interior of the Caribbean. Elsewhere, such discrepancies appear to reflect slip partitioning at an obliquely converging plate boundary. Hence we suggest the presence of a northern Lesser Antilles forearc (NLAF), which moves as a block distinct from both CA and NA plates. A difficulty for this model is the absence of geologic evidence for the boundaries of the presumed NLAF block. However, GPS data show that the motions of Martinique, Barbados, and Trinidad are similar to that of the Caribbean, suggesting that none are on the NLAF block, and strike-slip focal mechanisms of several shallow earthquakes suggest the presence of the NLAF's western boundary. If such a block exists and moving as suggested, it could affect kinematics at the northeastern corner of the CA plate, where a highly seismically active area, know as the Sombrero, may play a vital role. A NLAF block might also be relevant to the proposal of significant tsunami hazards from earthquakes in the Puerto Rico trench.
DE: 1209 Tectonic deformation (6924)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8158 Plate motions: present and recent (3040)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
DE: 8175 Tectonics and landscape evolution
SC: Tectonophysics [T]
MN: Fall Meeting 2005