This project is a continuation of a long-term NSF-sponsed effort to measure the present-day motion of the Caribbean plate and to determine the manner in which rigid plate motion is accommodated along the Caribbean-North America plate boundary near Hispaniola and Puerto Rico. The objectives include: (1) Construction of a Caribbean plate kinematic model using GPS-derived velocities from sites that span the Caribbean plate and to use the same velocities to test for non-rigidity of the Caribbean plate; (2) determination of how Caribbean-North America motion is partitioned by the faults that separate the two plates in the vicinity of Hispaniola and Puerto Rico, and ultimately, to extract information about the dynamics of this plate boundary by modeling elastic strain and extracting block rotations from the velocity field; (3) determination of the slip rate and level of elastic strain accumulation along the Septentrional fault in northern Hispaniola, which has not experienced a major earthquake in more than 700 years despite geologic evidence for significant slip over the past several thousand years. Occupations in 1986, 1994, and 1995 of a GPS network spanning the Caribbean-North America plate boundary have set the stage for determinations of site displacements that should resolve these questions, and sufficient time has now elapsed so that additional measurable (ranging from 10-100 millimeters) displacements have occurred within the exisiting network. The proposed work will include a reoccupation of the existing sites as well as densification and modest expansion of the network.
