Collaborative Research: Active Out-of-Sequence Thrusting in the Fila Costena Thrust Belt, Pacific Costa Rica

9909699 Fisher

9909375 Gardner

It is now widely recognized that convergent margins can experience accretion or subduction erosion with rates that depend on a variety of factors. The processes by which accretionary wedges grow are well documented, however the processes by which accretionary wedges erode are more enigmatic. This project will examine the Pacific Coast of Costa Rica and evaluate the current rates and the total shortening associated with active thrust faults in the inner fore arc of the Middle America Trench-faults that allow subduction erosion through underthrusting of the outer fore arc. Results will be used to evaluate whether there has been an arcward shift in the location of rapid shortening from the toe to the interior of the wedge for this area of rough crust and shallow subduction. This work is expected to increase knowledge about how accretaionary wedges erode.