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A seismic source model for Puerto Rico, for use in probabilistic ground motion hazard analyses

By
Roland C. LaForge
Roland C. LaForge
1
U.S. Bureau of Reclamation, Seismotectonics and Geophysics Group, Box 25007, D-8330, Denver Federal Center, Denver, Colorado 80225, USA
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William R. McCann
William R. McCann
2
Earth Scientific Consultants, Westminster, Colorado 80021, USA
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Published:
January 01, 2005

Here we present a seismic source model for Puerto Rico, designed for use in probabilistic ground motion hazard analyses. The model consists of characterizations of known on- and offshore faults and their estimated geometries, the magnitudes of maximum earthquakes, one or more recurrence models for each fault, and activity rates for randomly occurring upper-crustal seismicity beneath the island. Slip rates for faults in the Mona and Anegada Passages were estimated by the allocation of GPS-based regional horizontal geodetic vectors onto appropriate groupings of faults. Rates for other sources were based on GPS vectors or empirical fits to Puerto Rico Seismic Network (PRSN) data.

Hazard curves for peak horizontal acceleration were computed by using the model for the four corners of the island. The hazard appears to be greatest in the western part of the island, which is closer to the more active sections of the two subduction zones and faults of the Mona Passage extensional regime. To the east the hazard is less because of presumed lower coupling between the North America and Puerto Rico–Virgin Islands microplate, and because of dispersion of relative motion at the Muertos subduction zone onto faults in the Anegada Passage and the Investigator faults south of the island. Recommendations for further work include further development of attenuation parameters, refinement of the local seismicity catalog, and further investigations into faults on and near the island.

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Contents

GSA Special Papers

Active Tectonics and Seismic Hazards of Puerto Rico, the Virgin Islands, and Offshore Areas

Paul Mann
Paul Mann
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Geological Society of America
Volume
385
ISBN print:
9780813723853
Publication date:
January 01, 2005

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