The GPS survey performed in the Dominican Republic in October 2003, one month after a M6.5 earthquake struck the region of Puerto Plata, allowed us to resurvey 12 geodetic benchmarks previously measured with GPS in 1999 and 2001. These 12 sites are the northern third of a 36-site GPS network that covers the Dominican Republic. We also used GPS data from 4 continuous GPS stations operated by the Dominican Department of Justice.
We find significant and reliable coseismic displacements at 4
sites located within 50 km of the epicenter. The coseismic
displacements are consistent with a rupture dipping shallowly
to the southwest, with pure thrust motion. Our preferred coseismic
model is a 11.5 km wide by 25 km long rupture plane striking in
a N149E direction and dipping 15
to the southwest, located
offshore at a depth of 2 to 6 km.
This source model is constrained by 4 geodetic sites only. Additional information from seismic data will be necessary to better constrain the slip on the fault and the location of the rupture plane.
In addition to quantifying surface coseismic displacements, this GPS campaign provides a third measurement epoch for 12 sites, with important implications for the measurement of long-term interseismic strain in Hispaniola. For the sites that experienced coseismic displacements, this dataset will allow us to correct for the coseismic offset for long-term strain estimation. For the sites that did not experience coseismic displacements, this campaign adds a third epoch directly useful for long-term strain estimation. This is particularly important for sites PEPE and CRIS, where various problems occurred during the 1999 and/or 2001 surveys.