Stress field in Costa Rica, Central America

We have relocated 1658 earthquakes which occurred in Costa Rica, and its vi cinity. These relocated earthquakes were then used to investigate the stres s and orientation of fault planes within the study area. The analysis was m ade using the polarities of first motion P-waves. We found that the subduct ion zone for Costa Rica is mainly characterized by thrust faulting, with so me areas also exhibiting a component of strike-slip motion. The intraplate Caribbean seismicity in central Costa Rica shows a predominant shallow left -lateral strike-slip faulting. In southern Costa Rica, the subduction of ve ry young oceanic lithosphere beneath the Caribbean plate (i.e. Panama Block ), enhanced by the collision and subduction of the Cocos Ridge, has produce d a highly compressive stress regime. This highly compressive regime is cha racterized by strike-slip faults oriented in a NE-SW direction, extending a ll the way from the Pacific margin into the back-arc, connecting with the N orth Panama Deformed Belt.