NSF EAGER: Pilot Study: Deep Electrical Structure of the Rio Grande Rift to Constrain Extent and Mechanisms of Rifting

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A wideband and long period magnetotelluric pilot experiment will be conducted across the Rio Grande Rift in Colorado and New Mexico in order to provide constraints on the thermal and rheological state of the lithosphere beneath this region of intra-continental extension. Important questions about continental rifting remain unresolved, including the role of magmatism, volatiles, and inherited lithospheric structure in the initiation and development of rifting. Recent seismic imaging studies show thinned crust and low seismic wavespeeds in the upper mantle beneath the Rio Grande Rift. New geodetic work confirms the low strain-rate environment of the region, and shows surprisingly broad and uniform deformation over an area far wider than the rift?s physiographic expression. Electrical conductivity models from the pilot magnetotelluric experiment will provide information complementary to seismic studies, and will be combined with seismic models can be used to assess the relative contribution of thermal and compositional heterogeneity to the rifting process. A comparison of results from northern and central rift segments will be used to assess extent and hypothesized northward propagation of the rift. The magnetotellurics pilot experiment will include two rift transects, and the results will be evaluated to assess the need for an experiment with expanded or modified array design. In addition to the societal importance of better understanding low strain-rate environments, this project will support a PhD student and will involve undergraduate researchers.