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Title: Electromagnetic (EM-60) survey in the Panther Canyon Area, Grass Valley, Nevada

Eight frequency domain electromagnetic soundings were measured over the Panther Canyon thermal anomaly in Grass Valley, Nevada. The data were collected with Lawrence Berkeley Laboratory's large moment horizontal loop system (EM-60). At the transmitter site located near the center of the thermal anomaly, square wave currents of up to 70 A were impressed into a fourturn 50 m radius coil at frequencies from 0.033 to 500 Hz. At the eight receiver sites, 0.5 to 1.5 km from the loop, magnetic fields were detected with a three-component SQUID magnetometer and vertical and radial magnetic field spectra were calculated. Data were interpreted with a computer program which fit filled spectra and associated ellipse polarization data to one-dimensional resistivity models and results were compared to interpretations from earlier dipole-dipole resistivity measurements. Comparison of these interpretations indicates fairly close agreement between the two, with both models clearly indicating the presence and dimensions of the conductivity anomaly associated with the thermal zone. Although the dc data was better able to resolve the high resistivity bedrock, the EM-data were able to resolve all major features without distortion at shorter transmitter receiver separations and in about one-third of the field time.
Authors:
; ; ;
Publication Date:
OSTI Identifier:
5139469
Report Number(s):
LBL-10993
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Technical Report
Research Org:
California Univ., Berkeley (USA). Lawrence Berkeley Lab.
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; NEVADA; ELECTROMAGNETIC SURVEYS; GEOTHERMAL EXPLORATION; RESISTIVITY SURVEYS; DATA ANALYSIS; GEOLOGIC STRUCTURES; GEOLOGY; GEOPHYSICS; MAGNETOMETERS; MAPS; SQUID DEVICES; ELECTRICAL SURVEYS; ELECTRONIC EQUIPMENT; EXPLORATION; FLUXMETERS; GEOPHYSICAL SURVEYS; MEASURING INSTRUMENTS; MICROWAVE EQUIPMENT; NORTH AMERICA; SUPERCONDUCTING DEVICES; SURVEYS; USA; WESTERN REGION Geothermal Legacy 150301* -- Geothermal Exploration & Exploration Technology-- Geophysical Techniques & Surveys