AN INVESTIGATION OF THE MAGNETOTELLURIC METHOD FOR DETERMINING SUBSURFACE RESISTIVITIES,
Abstract
A series of micropulsation recordings was made at two locations in the Delaware Basin of West Texas. Magnetotelluric resistivity soundings have been computed from this data in the range of 0.0003 to 10.0 cps. Considerable attention is devoted to the computation techniques involved, which include power spectrum analysis, digital prewhitening and alias filtering, and decimation. Horizontally stratified earth models are derived from the data with the aid of a computer program which calculates and plots apparent resistivity and phase curves, including source dimension effect, for up to a 40 layer model, allowing 12 parameter permutations. The models, which represent penetration depths from about 400 m to over 100 km, are compared with available geologic information. Source dimension effects are shown to be negligible for spatial wavelengths exceeding 600 km. An anisotropy in the data is investigated with the aid of a computer program which performs a virtual rotation of the measurement axes and determines the variation with frequency of the azimuth of apparent resistivity extremes. The source of the anisotropy seems to be in the basement rocks more than 6.4 km deep. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1966
- Accession Number
- AD0629071
Entities
People
- George H. Hopkins Jr.
- Harold W. Smith