Use of a Towed, Direct-Current, Electrical Resistivity Array for the Classification of Marine Sediments

摘要

The direct-current (DC) electrical resistivity method has been used for a variety of offshore geophysical, geotechnical investigations. Model studies indicate that the DC technique is feasible for sediment classification and layer structuring. A prototype array was built to test the hypothesis that such a technique can be used while in an underway mode in the marine environment. A 60 m, inverted Schlumberger array was towed both on and off the seafloor with electrode spacings appropriate for a penetration depth of 10 m below the seafloor. Three different bottom types, mud, gassy mud, and sand, were surveyed in the Mississippi Sound using the array. Ground truth was provided with an acoustic seafloor classification system, CTD casts, and numerous sediment cores. Data were analyzed using SUBVERT, a modification of a University of California, Berkeley, inversion routine adapted for an IBM-PC AT. Both the layering structure of the upper sediment and lateral variability of sediment types were adequately defined by the DC technique. Reprints. (rh)