Comparison of Dipole-Dipole Resistivity and Electromagnetic Induction Sounding over the Panther Canyon Thermal Anomaly, Grass Valley, Nevada

摘要

A comparison is made between the dipole-dipole resistivity method and electromagnetic sounding method based on surveys over a geothermal anomaly near Panther Canyon, Grass Valley, Nevada. Dipole-dipole data were taken in conjunction with large-scale geothermal studies in the area. Two orthogonal lines were measured over the heat flow anomaly and two-dimensional modeling was performed on the data. EM sounding data were taken with the Lawrence Berkeley Laboratory EM-60 system which is a large-moment, frequency-domain, horizontal-loop system. Relative to single 50-meter-radius transmitter coil, eight soundings were made with detectors at distances of 0.5 to 1.6 km from the loop. Interpreted results from the two surveys indicate substantial agreement in the depth to and thickness of a conductive zone that may be associated with the thermal anomaly. The dipole-dipole method is inherently better for resolving resistive basement beneath the conductive anomaly, and dc resistivity interpretation techniques are presently better to handle the complex two-dimensional geology. However, the EM method is far less labor intensive, requiring only one-third the field time for similar areal coverage. (ERA citation 05:030558)