Accession Number : AD0663283

Title :   A MAGNETOTELLURIC INVESTIGATION AN ELECTRICAL CONDUCTIVITY ANOMALY IN THE SOUTHWESTERN UNITED STATES.

Descriptive Note : Doctoral thesis,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE GEOPHYSICS LAB

Personal Author(s) : Swift,Charles Moore , Jr

Report Date : AUG 1967

Pagination or Media Count : 226

Abstract : Large scale magnetotelluric observations were made in the southwestern United States by combining telluric data from seven sites with Tucson geomagnetic observatory data. The use of the Tucson data as representative for the telluric recording sites is justified by a quantitative coherency study, which showed that the geomagnetic fluctuations of fifteen minute to diurnal periods in the southwest are characterized by horizontal wavelengths greater than 10,000 kilometers. The magnetotelluric data is analyzed for tensor apparent resistivities, principal directions, and two-dimensionality measures. The measured anisotropic apparent resistivities are interpreted in terms of inhomogeneous resistivity structure, using theoretical values obtained for two-dimensional models which took the known surface geology into account. The resulting interpretations show a high conductivity zone in the upper mantle of southern Arizona and southwestern New Mexico. Thus, the magnetotelluric evidence supports Schmucker's geomagnetic indication of increased conductivities. Partly because this region is characterized by high heat flow, these high conductivities are attributed to a zone of high temperatures. (Author)

Descriptors :   (*GEOMAGNETISM, TELLURIC CURRENTS), ELECTRICAL RESISTANCE, ANOMALIES, TEMPERATURE, THESES

Subject Categories : Geomagnetism
      Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE