This multidisciplinary study of forearc evolution examines the short term (years) and long term (thousands to millions of years) patterns of strain in the upper plate of a subduction zone that straddles the subducting Panama Fracture Zone, an active transform fault. The project goals are to test several hypotheses, including: 1) upper plate deformation is primarily a consequence of indentation tectonics related to Cocos Ridge collision; 2) the Fila Costena thrust belt is propagating laterally into Panama with the migration of the Panama Triple Junction; 3) the velocity field in the upper plate reflects Cocos Ridge collision, including shortening across the Fila Costena, shear/uplift across the onshore projection of the Panama Fracture Zone, and the elastic strain associated with the earthquake cycle. The research team is using structural analyses, Quaternary geologic mapping and dating, and geodetic GPS and modeling studies in an effort to integrate a long-term record of deformation with short-term indicators of kinematics to allow for assessment of rates and styles of deformation of the upper plate. Intersection of the leading edge of the Fila Costena thrust belt with a volcanic debris fan provides excellent timelines to constrain deformation. Radiocarbon and Optically Stimulated Luminescence dating of a superb flight of marine terraces on the Burica Peninsula yield an excellent record of late Quaternary deformation of the peninsula. Geodetic research of strain partitioning will determine the spatial and temporal patterns of short-term elastic strain.
Subduction zones are sites of the largest earthquakes on earth, with buildup of elastic strain along the plate boundary until release of this stored energy during earthquakes. By combining short-term and long-term indicators of deformation in the upper plate of the Middle America plate boundary, the elastic or recoverable strain that leads to earthquakes as well as the permanent strain that averages the effects of many earthquakes can be evaluated. This project specifically addresses the coupling attributes of the plate boundary in southern Costa Rica and southwestern Panama, with an assessment of the earthquake hazard of these regions. The project, under the direction of principal investigators from Pennsylvania State University and Trinity University, involves graduate and undergraduate students and scientific collaborations with Costa Rican and Panamanian researchers. The project is supported by the NSF Earth Sciences Division Tectonics Program and the NSF Office of International Science and Engineering.
