Geophysical Unit of Menlo Park, Calif.

In Cooperation with the Southern Nevada Water Authority (SNWA)

U.S. Geological Survey
Open-File Report 2007-1181
Version 1.0

Audiomagnetotelluric Data and Two-Dimensional Models from Spring, Snake, and Three Lakes Valleys, Nevada

By Darcy K. McPhee, Bruce A. Chuchel, and Louise Pellerin


Photo of field truck parked on the side of a lonely dirt road; scientist sitting beside vehicle, deep valley in middle ground, steep snow-covered peaks in background and a vulture flying over the scientist


Audiomagnetotelluric (AMT) data along thirteen profiles in Spring, Snake, and Three Lakes Valleys, and the corresponding two-dimensional (2-D) inverse models, are presented. The AMT method is a valuable tool for estimating the electrical resistivity of the Earth over depth ranges of a few meters to roughly one kilometer. It is important for revealing subsurface structure and stratigraphy within the Basin and Range province of eastern Nevada that can be used to define the geohydrologic framework of the region. We collected AMT data using the Geometrics StrataGem EH4 system. Profiles were 1.2 to 4.6 km in length with station spacing of 100-400 m. Data were recorded in a coordinate system parallel to and perpendicular to the assumed regional geologic strike direction. We show station locations, sounding curves of apparent resistivity, phase, and coherency, and 2-D models. The 2-D inverse models are computed from the transverse electric (TE), transverse magnetic (TM), and TE+TM mode data using the conjugate gradient, finite-difference method of Rodi and Mackie (2001). Preliminary interpretation of these models defines the structural framework of the basins and the resistivity contrasts between alluvial basin-fill, volcanic units, and carbonate/clastic rocks.

Download this report as a 47-page PDF file (of2007-1181.pdf; 7.9 MB).

Download Appendix A for this report; it is another 47 pages as a report as a 47-page PDF file (of2007-1181_appendix_a.pdf; 4.1 MB).

For questions about the content of this report, contact Darcy McPhee

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