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Collision versus sliver transport in the hanging wall at the Middle America subduction zone: Constraints from background seismicity in central Costa Rica
Geoscience Department, Indiana University of Pennsylvania, 114 Walsh Hall, Indiana, Pennsylvania 15705, USA
Geoscience Department, Indiana University of Pennsylvania, 114 Walsh Hall, Indiana, Pennsylvania 15705, USA
Engineering Geology Instituto Costarricense de Electricidad, Box 10032, San José -1000, Costa Rica
School of Geology, University of Costa Rica, Apartado 214-2060, San Pedro, Costa Rica
Earthquake focal mechanism solutions for 135 small-magnitude events are inverted for best fitting partial strain rate tensors that characterize contemporary strain in five areas that span the western margin of the Panama microplate in central Costa Rica. The results indicate the predominance of subhorizontal maximum stretching subparallel to the Middle America Trench (MAT) and provide constraints on the role of Cocos ridge collision at the MAT. The trajectory of maximum stretching changes ∼25°–45° over several tens of kilometers from the Central Costa Rica Deformed Belt (CCRDB) where it is nearly E–W to the area inboard of the Cocos ridge where it is NW–SE. This change suggests that background seismogenic deformation reflects the transition from the trailing edge of a fore-arc sliver to an area of the upper plate affected by ridge collision. This diffuse deformation may be localized, in part, on conjugate strike-slip faults of the CCRDB.
Received 6 June 2007; accepted 19 May 2008; published 1 July 2008.
Citation: (2008), Collision versus sliver transport in the hanging wall at the Middle America subduction zone: Constraints from background seismicity in central Costa Rica, Geochem. Geophys. Geosyst., 9, Q07S06, doi:10.1029/2007GC001711.
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