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Side-scanning sonar surveys of parts of the floor of the Santa Barbara Channel, California, carried out in March 1969 in connection with the U.S. Geological Survey's study of the oilspill area, provide the basis for an acoustic-geologic map of the area. Navigation during the field work was controlled closely and continuously by means of aircraft-tracking radar onshore that communicated with the ship by 2-way radio.

The side-scanning-sonar equipment consisted of a towed transducer housing a dual array of piezoelectric-crystal hydrophones, each 4 ft long, one operating at 27.5 khz and the other at 30 khz. These were triggered alternately with 0.5-m sec pulses at 1-sec intervals and scanned the bottom to ranges of 375 m on both sides of the track or in a single-channel mode to ranges of 750 m on one side or the other. The shipboard equipment included the electronic systems, power supply, and recorder, which displayed returns on linear sweeps of an intensity-modulated Alden helix recorder, 45 cm wide, printing 45 lines/cm of length on wet paper.

Features mapped include smooth bottom, rippled sand bottom, ledges of folded bedrock, drilling towers, pipelines, and features of unknown origin. Sonar records delineate changes in strike of the north-dipping strata on the flanks of the east-west-trending Rincon anticline, and identify a structural depression along the anticlinal crest at long. 119°40^primeW.

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