Geodetic and seismic constraints on some seismogenic zone processes in Costa Rica

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Read Full Article (file size: 2273069 bytes) Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, B11403, doi:10.1029/2003JB002931, 2004 Geodetic and seismic constraints on some seismogenic zone processes in Costa Rica Edmundo Norabuena Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, Florida, USA Timothy H. Dixon Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, Florida, USA Susan Schwartz Earth Sciences Department, University of California, Santa Cruz, California, USA Heather DeShon Earth Sciences Department, University of California, Santa Cruz, California, USA Andrew Newman Earth Sciences Department, University of California, Santa Cruz, California, USA Marino Protti Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional, Heredia, Costa Rica Victor Gonzalez Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional, Heredia, Costa Rica LeRoy Dorman Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA Ernst R. Flueh Leibniz Institut fur Meereswissenshaften, Forschungszentrum fur Marine Geowissenschaften (IFM-GEOMAR) and SFB574 Christian-Albrechts Universitat, Kiel, Germany Paul Lundgren Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA Fred Pollitz U.S. Geological Survey, Menlo Park, California, USA Dan Sampson Earth Sciences Department, University of California, Santa Cruz, California, USA Abstract New seismic and geodetic data from Costa Rica provide insight into seismogenic zone processes in Central America, where the Cocos and Caribbean plates converge. Seismic data are from combined land and ocean bottom deployments in the Nicoya peninsula in northern Costa Rica and near the Osa peninsula in southern Costa Rica. In Nicoya, inversion of GPS data suggests two locked patches centered at 14 ± 2 and 39 ± 6 km depth. Interplate microseismicity is concentrated in the more freely slipping intermediate zone, suggesting that small interseismic earthquakes may not accurately outline the updip limit of the seismogenic zone, the rupture zone for future large earthquakes, at least over the short (∼1 year) observation period. We also estimate northwest motion of a coastal “sliver block” at 8 ± 3 mm/yr, probably related to oblique convergence. In the Osa region to the south, convergence is orthogonal to the trench. Cocos-Caribbean relative motion is partitioned here, with ∼8 cm/yr on the Cocos-Panama block boundary (including a component of permanent shortening across the Fila Costeña fold and thrust belt) and ∼1 cm/yr on the Panama block–Caribbean boundary. The GPS data suggest that the Cocos plate–Panama block boundary is completely locked from ∼10–50 km depth. This large locked zone, as well as associated forearc and back-arc deformation, may be related to subduction of the shallow Cocos Ridge and/or younger lithosphere compared to Nicoya, with consequent higher coupling and compressive stress in the direction of plate convergence. Received 5 December 2003; accepted 4 August 2004; published 9 November 2004. Keywords: seismogenic zone; Costa Rica; geodetic and seismic. Index Terms: 8150 Tectonophysics: Plate boundary—general (3040); 8102 Tectonophysics: Continental contractional orogenic belts; 1208 Geodesy and Gravity: Crustal movements—intraplate (8110); 1243 Geodesy and Gravity: Space geodetic surveys; 7230 Seismology: Seismicity and seismotectonics. Read Full Article (file size: 2273069 bytes) Cited by Citation: Norabuena, E., et al. (2004), Geodetic and seismic constraints on some seismogenic zone processes in Costa Rica, J. Geophys. Res., 109, B11403, doi:10.1029/2003JB002931. Copyright 2004 by the American Geophysical Union.

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