This was my dissertation topic. It utilized both seismic data (from two crustal refraction lines) and magnetotelluric data (from a detailed survey done by Mobil Oil Company) in west Texas. I found that regions of low seismic velocities coincide with regions of low electrical resistivity at mid-crustal depths and interpreted the coincidence as being due to a small amount of interstitial fluids at those depths. Fluids in faults, fractures, and permeable rock in the crust also appear to be the best explanation of regional variations of seismic Q that I find in recent and current studies.

Mitchell, B.J., and M. Landisman, Electrical and seismic properties of the Earth's crust in the southwestern Great Plains of the U.S.A., Geophysics, 36, 363-381, 1971.

Landisman, M., S. Mueller, and B.J. Mitchell, A review of evidence for velocity inversions in the crust, in Am. Geophysical Union Monograph 14, The Structure and Physical Properties of the Earth's Crust, edited by J.G. Heacock, 11-34, 1971.

Mitchell, B.J., and M. Landisman, Geophysical measurements in the southern Great Plains, in Am. Geophysical Union Monograph 14, The Structure and Physical Properties of the Earth's Crust, edited by J.G. Heacock, 77-93, 1971.