WRRCTR No.169 Electrical Resistivity Investigation of Schofield High-Level Water Body, O'ahu, Hawaii

Abstract

The high-level water body beneath the Schofield Plateau was studied using 19 Schlumberger resistivity soundings and three gradient profiles. The soundings were interpreted for one-dimensional models and the results were then improved upon by considering two-dimensional models for the soundings and gradient profiles. One of the most significant contributions of the study is that gradient profiling was successfully used in conjunction with sounding for the deep investigation. Gradient profiling has been traditionally applicable mainly for shallow investigations, particularly in mineral exploration. The southern boundary is found to be very close to Kunia Camp on the southwest part of the Schofield Plateau and strikes N64°E; the northern boundary strikes N54°E. Both boundaries appear to be dike related, and in the north (particularly in the northeast part of the Schofield Plateau) the dikes occur at shallow depths. The recent geologic history of the Waianae and Koolau volcanoes, as understood today, does not readily explain the presence of shallow dikes in this region. It is interesting to note, however, that the existence of such shallow intrusives fits well with an earlier explanation, thus far largely unsubstantiated, of different episodes of Koolau volcanism.