Subduction-Related Stress Field in Central America and Intraplate Stress in Costa Rica

Date: 4/24/2019

Time: 04:15 PM

Room: Cascade II

Along-strike stress variations in subduction zones reflect along-strike variations in subduction processes, and down-dip stress variations illuminate the driving mechanisms of convergence. Using more than 2500 moment tensors, we systematically map the 3D stress field along the Middle America Subduction Zone from southern Mexico to Panama. Results in the oceanic plate are readily interpreted as the hallmarks of slab pull. Margin-normal extension near the trench reflects slab bending, and events below 50 km reveal down-dip extension. By contrast, trench-perpendicular shortening to a few tens of km depth results from slab-continent coupling. As previously documented, the subducting plate shallows abruptly beneath central Costa Rica, and this geometric change has a profound impact on the continental stress field. Grossly, escape-style tectonics manifest as monotonic counterclockwise rotation of maximal compression from NE–SW in Panama in southern Central America, to NNW­–­SSE in Guatemala in northern Central America, with convergence-parallel stress in central Costa Rica, and a progression from transpression in Panama to thrust faulting in Costa Rica and back to strike-slip and even normal faulting in Nicaragua and northward. In Costa Rica, higher data density reveals a complex, roughly toroidal intraplate stress field. The reason for this complexity is not presently understood, but it may derive from kinematic interactions within the Central Costa Rica Deformed Belt and/or from topographical and rheological heterogeneities including seamounts and the Cocos Ridge of the underthrusting plate.

Presenting Author: Will Levandowski

Authors