DEEP RESISTIVITY RESULTS FROM DC GROUND TESTS AT HOOVER DAM.
Scientific rept. for Jan-Feb 64,
GEOSCIENCE INC CAMBRIDGE MASS
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A deep crustal resistivity survey was conducted in the California, Nevada, Arizona and Utah area centered roughly about Las Vegas. The survey revealed that layered interpretation appears to be of value in the area. Regional and local geologic variations were also reflected in the results. The interpreted model of the electrical properties of this area is a three layer case. The upper layer has a low resistivity on the order of 10ghms-m, and varies in thickness from a few hundred meters in Southern California to 1 or 2 km to the northeast. The second layer is 26 to 30 km thick, increasing to the northeast. The resistivity of the second layer varies from about 3,000 ghms-m to 20,000 ghms-m, increasing to the southwest. The Mohorovicic discontinuity forms the base of the second layer, with the underlying upper mantle having a conductivity at least an order of magnitude greater than that of the second layer. Rugged topography in the area causes local variations in thickness of the conductive valley fill. This causes sufficient scatter in the data that definitive interpretation at the long separations necessary would be virtually impossible without other geophysical data. Author