Geophysical surveys -- Island of Molokai, Hawaii

Nance, Tom
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Blackhawk Geosciences, Inc.
Tom Nance Water Resource Engineering
This report covers the results of geophysical surveys conducted by-Blackhawk Geosciences, Inc. (BGI) for Alpha U.S.A., Inc. (Alpha) on the island of Molokai, Hawaii. The field work was performed between February 15 and March 4, 1990. Three separate geophysical surveys were used by BGI. The geophysical surveys conducted and their individual objectives are as follows: 1. Seismic refraction surveys were utilized to map the depth to volcanic rocks and the seismic velocity distribution of the rock units in the area of Kamkaipo located in the southwest corner of the island. The seismic velocity distribution was subsequently correlated to mode and ease of excavation. 2. Gravity surveys were performed to outline intrusive (dense) bodies which may form a base to dike-impounded ground water and may be a source of vertical impounding dikes. 3. Time domain electromagnetic CTDEM) surveys were conducted to map the thickness of the fresh to brackish water lens and the location of dike-impounded ground water to better outline the geohydrologic system of Molokai's central aquifer area. In addition, work was performed to further delineate areas of relatively thick brackish water lenses identified in the previous TDEM survey in the western portion of Molokai. The report is written in two parts. The first part consists of the TDEM and gravity surveys which address the mapping of ground water resources on Molokai, and the results of the seismic survey are contained in the second portion.
groundwater, TDEM, Molokai, Hawaii
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