DIPOLE-DIPOLE RESISTIVITY SURVEY OF A PORTION OF THE COSO HOT SPRING HOT SPRINGS KGRA INYO COUNTY, CALIFORNIA

摘要

A detailed electrical resistivity survey of 54 line-km was completed at the Coso Hot Springs KGRA in September 1977. This survey has defined a bedrock resistivity low at least 4 sq mi (10 sq km) in extent associated with the geothermal system at Coso. The boundaries of this low are generally well defined to the north and west but not as well to the south where an approximate southern limit has been determined. The bedrock resistivity low merges with an observed resistivity low over gravel fill east of Coso Hot Springs.nA comp1ex horizontal and vertical resistivity structure of the surveyed area has been defined which precludes the use of 1ayered-earth or two-dimensional interpretive model s for much of the surveyed area. In general the survey data indicate that a 10 to 20 ohm-meter zone extends from near surface to a depth greater than 750 meters within the geothermal system. This zone is bordered to the north and west by bedrock resistivities greater than 200 ohm-meters and to the south by bedrock resistivities greater than 50 ohm-meter s. A combination of observed increases in:1) fracture density (higher permeability), 2) alteration (high clay content), and 3) temperatures (higher dissolved sol i d content of ground water) within the bedrock low explain its presence.