Role of Rheology and Water in Rapid Mantle Flow: 3D Numerical Models of the Costa Rica-Nicaragua Subduction Zone

Jadamec Margarete A, Mystic CT

Investigators

Abstract

Dr. Margarete Jadamec is awarded an NSF Earth Science Postdoctoral Fellowship to carry out a research and education plan at Brown University. Dr. Jadamec will investigate the role of 3D variations in slab shape and rheology, including the effects of variable water content in the mantle wedge and a strain-rate dependent viscosity, on the rate and direction of mantle flow in subduction zones. To study this process, Dr. Jadamec will construct observationally based 3D numerical models of the Costa Rica-Nicaragua portion of the Cocos-Caribbean plate boundary. As part of the NSF MARGINS TUCAN experiment, the Costa Rica-Nicaragua subduction zone has been well imaged seismologically. This information will be used to construct the slab geometry and overriding plate structure, as well as to constrain the along strike changes in water and/or melt content within the mantle wedge. Subduction zone parameters in the 3D numerical models will be systematically varied to gain insight into the underlying physics that govern mantle flow in subduction zones. The predicted 3D mantle velocity vector field, and calculated infinite strain axes, will be compared to mantle flow rates inferred from geochemical studies and observations of seismic anisotropy, which presently suggest a fast and spatially complex velocity field in the mantle wedge beneath Costa Rica and Nicaragua. These 3D numerical models will shed light on the apparent trench parallel flow beneath Costa Rica and Nicaragua, which to date lacks a clear, quantitatively-tested explanation. Rapid 3D mantle flow has implications for the timescales of deformation in subduction zones and the transport of geochemical signatures within the mantle wedge. For the educational component, Dr. Jadamec will incorporate 3D immersive virtual reality (VR) laboratory exercises into undergraduate geophysics and tectonics courses at Brown University. The 3D VR will be used to teach inherently 3D concepts such as the relative dimensions and volumes of the Earth's core, mantle, and lithosphere, the geometry of Wadati-Benioff zones, the spatial connections in triple junctions, and seismic tomography. This work will be done in collaboration with Brown University's Center for Computation and Visualization, which has both a CAVE and a 3D display wall.