HR: 0800h
AN: GP41B-0868    [Abstracts]
TI: 1D Forward Modeling of Regional Electrical Conductivity Structure Using Mineral Physics Constraints and Seismic Observables.
AU: * Toffelmier, D A
EM: dan.toffelmier@asu.edu
AF: Arizona State University, Department of Geological Sciences P.O. Box 871404, Tempe, AZ 85287-1404 United States
AU: Tyburczy, J A
EM: jim.tyburczy@asu.edu
AF: Arizona State University, Department of Geological Sciences P.O. Box 871404, Tempe, AZ 85287-1404 United States
AU: Du Frane, W L
EM: wyatt.dufrane@asu.edu
AF: Arizona State University, Department of Geological Sciences P.O. Box 871404, Tempe, AZ 85287-1404 United States
AU: Roberts, J J
EM: roberts17@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Ave. L-201, Livermore, CA 94550 United States
AB: Regional magnetotelluric (MT) studies are forward modeled to include new and relevant mineral physics constraints and seismic observations. Two MT studies; Superior Craton, Canada (Schultz et al., 1993) and the French Alps (Tarits et al., 2004) are forward modeled using recent olivine conductivity measurements made by Xu et al. (2000), and Du Frane et al. (2005) with an elevated electrical conductivity zone (-2.5 < log(σ - S/m) < -2) between approximately 200-400 km depth. The onset of this elevated conductivity zone roughly corresponds with the Lehmann seismic discontinuity and could signal a change in the deformation mechanism in major mantle minerals, or perhaps, the presence of mantle water (Karato 1992). Models have also been developed that incorporate a thin melt layer immediately above the 410 km seismic discontinuity, as proposed by Bercovici and Karato (2003). Although the exact electrical conductivity and thickness of this melt layer are quite speculative, a 10 km thick layer with a conductivity of approximately 1 order of magnitude or greater than that of the transition zone would be consistent with experimental constraints and should be detectable by long period MT measurements. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract W-7405-ENG-48.
DE: 1515 Geomagnetic induction
DE: 3914 Electrical properties
DE: 5109 Magnetic and electrical properties (0925)
DE: 8162 Rheology: mantle (8033)
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005