. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography deeply buried thick deposit (fig. 14) . Thin deposits that are deeply buried cannot be resolved by present systems. In either case, the deposit sought must be associated with density and sound velocity dis- continuities in order to be detected by seismic reflection. A variety of sound sources exists differing in their acoustic char- acteristics (Kramer et al., 1968; Ocean Industry, 1968). The low frequency energy component of explosive sources such
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography deeply buried thick deposit (fig. 14) . Thin deposits that are deeply buried cannot be resolved by present systems. In either case, the deposit sought must be associated with density and sound velocity dis- continuities in order to be detected by seismic reflection. A variety of sound sources exists differing in their acoustic char- acteristics (Kramer et al., 1968; Ocean Industry, 1968). The low frequency energy component of explosive sources such as TNT, Nitromon, and Geofex (du Pont Blasters Handbook) can achieve penetration of several tens of kilometers at the expense of resolution. Explosive charges from about 250 grams up to thousands of kilograms are generally prepared and thrown over-the-side manually, which limits the repetition rate. Other types of sources repeat automatically at faster repetition rates provid- ing more sampling points to delineate reflecting interfaces which can change markedly over distances of one kilometer. Gas mixture sources generate explosions within long rubber hoses producing low peak frequency (less than 10 Hertz), broad bandwidth signals with intermediate resolu- tion up to about 6 kilometers penetration in unconsolidated rocks. The Vibroseis source hydraulica1ly drives metal plates to produce low fre- quency (less than 100 Hertz), broad bandwidth signals which can be shaped and programmed to yield deep penetration with fair resolution. The pneu- matic source or air gun suddenly injects a bubble of high pressure air (about 2000 pounds per square inch or 1^0 kilograms per square centime- ter) into the water which commences to oscillate generating subsidiary. Figure 14. A low resolution, deep penetration seismic reflection profile shows salt domes the continental shelf off West Africa (From fig. 7 ) . ( (s Te 5 k had mpl ilomet ed) be eton , ers) nea th 1970 , 111. Please note that thes
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