During August 27, 28, and 29, 1956, Research Vessel Bear and a shooting boat were used in a seismic refraction survey of Narragansett Bay, Rhode Island, to determine the depth to bedrock beneath the bay and the subbottom geological conditions. Twenty-nine refraction profiles were established along about 18 miles, from the southern end of the West Passage of the bay to the northern end of the bay.
Using a floating cable with 12 detectors at 100-foot intervals and conventional seismic prospecting-recording equipment 282 seismograms were obtained. The results show that a large portion of the bay is underlain by two prominent high-velocity layers. The depth to the first layer is between 60 and 200 feet and the velocity of the layer ranges between 10,000 and 14,000 ft/sec. The depth to the second layer is generally between 150 and 500 feet, and the velocity ranges between 16,000 and 20,000 ft/sec. It is suggested that the first layer corresponds to a thin layer of Carboniferous rocks, and the second to a crystalline basement complex which persists at shallow depths.