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Adel A. R. Zohdy

Publications and source records attributed to Adel A. R. Zohdy.

42 records · Page 3Linked to original sources
USGS1969

Application of deep electrical soundings for groundwater exploration in Hawaii

Forty-five resistivity soundings, using Schlumberger and equatorial dipole electrode configurations, were made on the islands of Oahu and Hawaii to determine the applicability of direct current resistivity methods for locating freshwater aquifers in the State of Hawaii. The soundings were made on the northwestern part of the island of Oahu near the town of Waialua and on the island of Hawaii on the "saddle" area near Pohakuloa and Humuula. Interpretation of 32 sounding curves obtained on the island of Oahu indicates that it is possible to correlate five stratigraphic units underlain by a vesicular basalt basement and that the determination of the approximate depth to the freshwater-saline-water interface within the basalt is feasible. Two of these Schlumberger soundings with electrode spacings AB/2 reaching 6000 ft yielded sounding curves of the maximum and minimum types whose terminal branches asymptotically approach a resistivity of about 30 ohm, which is believed to be the true resistivity of basalt saturated with sea water. Near the town of Waialua the aquifer is a coral zone as well as parts of the weathered vesicular basalt basement. On the island of Hawaii, near Pohakuloa, an exploratory well drilled in basalt to a depth of 1001 ft (prior to the resistivity survey) proved to be dry. Interpretation of thirteen deep soundings made with Schlumberger and equatorial arrays suggests that the minimum depth to a conductive layer, which may represent basalt saturated with fresh water, is about 2700 ft below land surface. The groundwater appears to be dike impounded.

Hawaii↗
USGS1969

The use of Schlumberger and equatorial soundings in groundwater investigations near El Paso, Texas

Electrical soundings using the symmetric AMNB Schlumberger and the bipole-dipole equatorial arrays were made along two profiles near El Paso, Texas, in support of a groundwater exploration program which included seismic refraction and gravity surveys. Electrode spacings (AB/2 or R) reaching 12,000 ft allowed exploration to depths of about 7000 ft. Geoelectrical information on the subsurface materials was augmented by sounding with the bilateral equatorial configuration and by transforming Schlumberger curves into dipole-polar sounding curves with formulas developed by Al'pin and by Tsekov. The bilateral equatorial sounding curves were found useful for detecting the direction of dip of highly resistive bedrocks whereas transformed sounding curves were used to evaluate the average longitudinal resistivity, and hence the depth, to the "electric basement." A few of the Schlumberger sounding curves were either clearly or subtly distorted by nonhorizontal geologic structures. The interpretation of these sounding curves illustrates the requirement for careful analysis in processing electrical prospecting data obtained over complex geologic conditions. The interpretation of a combined Schlumberger-equatorial sounding curve, which did not agree with the preliminary interpretation of seismic refraction data, was confirmed to be correct by data from a test well drilled to a depth of 4363 ft. The application of electrical sounding data in the El Paso area furnished valuable information on the depth to fresh-water-saltwater interfaces and on the depth to highly resistive impervious bedrocks.

Texas↗
USGS1968

Ground-water exploration using the resistivity method on the Hawaiian Islands of Oahu and Hawaii

Thirty-six resistivity soundings were made on the islands of Oahu and Hawaii to determine the applicability of galvanic resistivity methods for locating fresh-water aquifers in the State of Hawaii. Soundings were made on the northwestern part of the island of Oahu near the town of Waialua and on the island of Hawaii on the "saddle" area near Pohekuloa and the Humuula sheep station. On Oahu, the geoelectrical study indicates that correlation among four stratigraphic units underlain by a vesicular basalt basement is possible. The electrical soundings indicate that it is feasible to determine the approximate depth to the fresh-saline water interface within the basalt. Two Schlumberger soundings with electrode spacings, AB/2, reaching 6,000 feel give sounding curves of the maximum and minimum type whose terminal branches indicate that the true resistivity of basalts saturated with sea water, in the survey area on Oahu, is about 30-40 ohm-m. On the island of Hawaii, an exploratory well drilled in basalt to a depth of 1,001 feet proved to be dry. In the area of this well, two deep soundings were made using the Schlumberger and the equatorial arrays. Although additional soundings at various orientations and larger spacings are needed, there appears to be a conductive layer below 1,600 feet which may represent basalt saturated with fresh water.

Hawaii↗