HR: 10:50h
AN: S52A-03    [Abstracts]
TI: The Muertos Subduction Zone as a Major Earthquake and Tsunami Hazard for Puerto Rico
AU: * McCann, W R
EM: wrmccann@comcast.net
AF: Earth Scientific Consultants, 10210 West 102nd Avenue, Westmisnter, CO 80021, United States
AB: A revised catalog of 25 years of locally recorded earthquakes located using newly developed 1-D and 3-D velocity models allows us to better understand the spatial distribution of these events and their relation to known tectonic structures. In map view, the relocated events still show a pattern generally lacking in lineations that might be related to crustal faults. However, the previous cloud of crustal events in vertical cross sections now display a clear northerly dipping seismic zone as shallow as 10 km depth along the island's south coast extending to 40 km depth along the north coast of the island. This dipping seismic zone is interpreted as the Muertos Megathrust along which buoyant Caribbean Plate is obliquely underthrust beneath Puerto Rico. 3-D velocity anomalies associated with the region of high seismicity in western Puerto Rico confirm subducted Caribbean crust and lithosphere. The dipping seismic zone is seen best in SW Puerto Rico but also extends to the easternmost part of the island. Seismicity and historic earthquakes in the Dominican Republic also indicate the presence of the Muertos Megathrust beneath the SE part o that country. A large earthquake in 1751 generated a damaging tsunami. These new data suggest a new paradigm for earthquake hazards from "crustal" or "shallow" earthquakes in Puerto Rico. That is, after removing events associated with the dipping megathrust, little "random crustal seismicity" is left in the crustal wedge above the plate interface, and the amount and location of random crustal events depends heavily upon exactly which events are chosen to be part of the megathrust seismicity.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: 2007 Joint Assembly