HR: 1340h
AN: S23B-0238    [Abstracts]
TI: The Central Costa Rica Deformed Belt: Neotectonics of the Eastern Segment
AU: Montero, W
EM: wmontero@geologia.ucr.ac.cr
AF: Universidad de Costa Rica, Escuela Centroamericana de Geologia, Red Sismol¢gica Nacional (ICE-UCR), Apartado 2-14 2060, San Jose, N/A Costa Rica
AU: * Linkimer, L
EM: linkime1@msu.edu
AF: Michigan State University, Department of Geological Sciences, 206 Natural Science Building, East Lansing, MI 48824-1115 United States
AB: The Central Costa Rica Deformed Belt (CCRDB) is an east-west system of neotectonic faults, located in the central part of Costa Rica. The Turrialba and Siquirres regions, in the eastern segment of this zone, are characterized predominantly by strike-slip faults. Based on the geometry of faulting, six different faults systems were recognized: Atirro-Rio Sucio, Navarro, Kabebeta, Pacuare, Siquirres-Matina and the Irazu-Turrialba volcanoes. Quaternary volcanic and sedimentary deposits were found to be deformed by the main faults. Linear valleys, deflected streams, shutter ridges, scarps, pressure ridges, sag ponds, and offset streams were also identified from the geomorphologic and remote sensing studies along the traces of the main faults. During the period 1992-2002, the seismicity was characterized by shallow earthquakes (< 19.6 km) and low magnitudes (1.7-4.4 Md and 1.0-4.1 ML). 359 seismic events in the study area were relocated. They were selected from the data base of the National Seismological Network of Costa Rica. The distribution of the relocated epicenters suggests that the following faults are active: Siquirres, Irazu, Guayabo, Navarro, Lajas Turrialba, Azul, Tucurrique, Pacuare, and Kabebeta. There is a strong relationship between the orientation of the faults and the type of displacement. Right lateral faults are oriented N30-50W, left lateral faults are N40-50E, normal faults are N0-20E, and reverse faults are N70W. The geometry of faulting suggests that the crustal deformation is controlled by a maximum compressive horizontal stress N0-20 E, which is related to the shallow subduction of the Cocos Ridge beneath southeastern Costa Rica.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8107 Continental neotectonics (8002)
DE: 8111 Continental tectonics: strike-slip and transform
DE: 8150 Plate boundary: general (3040)
SC: Seismology [S]
MN: Fall Meeting 2005