Neotectonic faulting and forearc sliver motion along the Atirro-Ro Sucio fault system, Costa Rica, Central America
Walter Montero P. et al., Geological Sciences Research Center, University of Costa Rica, San Jos, Costa Rica; Corresponding author: Sarah Kruse, Dept. of Geology, University of South Florida, Tampa, Florida 33620, USA. Posted online 22 Feb. 2013; http://dx.doi.org/10.1130/B30471.1.
Two important questions about the Cocos-Caribbean subduction zone of Costa Rica are how trench-parallel forearc motion is accommodated and what drives forearc sliver motion. This work by Walter Montero P. and colleagues provides critical constraints on the former and lays the foundation for exploring the latter. It documents a network of northwest-striking right-lateral strike slip faults that appears to mark the northern boundary of an upper-plate sliver moving NW relative to the Caribbean plate. Despite high erosion rates and deep weathering, the fault system includes pull-apart basins with preserved normal fault scarps and tilted hanging-wall buttress unconformities, pressure ridges, displaced and beheaded drainages, sag ponds, and fault-controlled upland valleys. Montero and colleagues integrate geomorphic observations with outcrop-scale bedrock fault kinematic and earthquake focal mechanism data to map the active through-going fault zone. The mapping reveals that the fault system traverses the active volcanic arc from NW to SE and connects to an area of high uplift rate in the inactive Talamanca magmatic arc, where the faults are
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