An electrical resistivity survey of the Puna and Kau districts, Hawaii County, Hawaii

Abstract

An electrical resistivity survey was carried out over the Kilauea shield area in Puna and the Kau district of the Island of Hawaii during the period from May through July, 1973. for the purpose of locating areas favorable for the presence of geothermal reservoirs. The technique employed was the dipole mapping technique, which is widely used as a reconnaisance method in prospecting for geothermal reservoirs. It was found that the flanks of Mauna Loa are underlain by rocks of high resistivity, and that such rocks probably extend into the Puna area along the projection of an ancient rift zone of the volcano. Mauna Loa. The high resistivities probably represent the presence of dense, cool dike complexes, so that this portion of the area is unlikely to have such prospect for geothermal development. On the other hand, resistivities as low as two ohm-meters were mapped along the lower part of the East Rift of Kilauea. Assuming reasonable values of porosity and water salinity, such resistivity values are compatible with the presence of thermal waters with temperatures above 1800 C., probably extending to a depth of two kilometers below sea level. Measurements made around the summit area of Kilauea confirm the existence of a brackish-water geothermal system along the south side of Kilauea Caldera, in the vicinity of the Kilauea Geothermal Test Well. It is recommended that further detailed work be carried out in the vicinity of the areas with anomalously low resistivity in Puna, so that the best location for a test hole may be found.