9616450 Wannamaker This award provides partial support for the upgrade of a portable magnetometer system and the acquisition of associated field equipment by the University of Utah that will become part of a centrally managed pool of equipment and made available to US researchers for field deployment in projects using the magnetotelluric (MT) technique to image the Earth's deep interior structure. The University of Utah is committed to providing the remaining funds necessary to acquire the equipment. Remote sensing of the Earth's crust and upper mantle using MT methods recently has made significant progress in producing images of internal structures with good spatial resolution and with content (electrical conductivity) that is distinct from seismic images (seismic velocities). The MT method makes use of the time-dependent natural electromagnetic fields (EM) induced inside the Earth by the variations of the Earth's external geomagnetic field. The induced electric (telluric) currents diffuse into the Earth and are scattered back from heterogeneities in the electrical resistivity structure. The complex, frequency dependent, relationship between the horizontal magnetic and electric fields at the surface is called the MT impedance and can be inverted to solve for the resistivity (or conductivity) structure of the interior. Conductivity properties of the interior are of considerable interest because they depend strongly on the presence of conducting ionic fluids or melts which are difficult or impossible to detect with other remote sensing techniques. ***
