. The Earth beneath the sea : History . BOTTOM REFLECTION ^ BEDROCK =^EFLECTlON 200 Fig. 18. A recording of multiple-bottom reflections anid a complex reflection from preglacial bedrock in Narragansett Bay, Rhode Island. Note that the bedrock reflection is weakened so as not to record beneath the strongly reflecting portion of the bottom. (Fink and Bunce.) number of straightforward observations have been made by now which must be understood to interpret a recording properly; these will be discussed in the order that they might well be taken up in analyzing a seismic survey. A graphic recorder
. The Earth beneath the sea : History . BOTTOM REFLECTION ^ BEDROCK =^EFLECTlON 200 Fig. 18. A recording of multiple-bottom reflections anid a complex reflection from preglacial bedrock in Narragansett Bay, Rhode Island. Note that the bedrock reflection is weakened so as not to record beneath the strongly reflecting portion of the bottom. (Fink and Bunce.) number of straightforward observations have been made by now which must be understood to interpret a recording properly; these will be discussed in the order that they might well be taken up in analyzing a seismic survey. A graphic recorder will bring out correlated signal sequences A\'hich have nothing to do with the profiling (except to degrade it). Typical occurrences are power-line cross-feed and rhythmic noise from ship's engines or propellers. These are best identified when the recording is made. It is usually a simple matter to shut off the sound pulse long enough to distinguish such noises. They should, of course, be eliminated or reduced if possible. In shallow-water surveying an echo-sounder record often contains echo sequences of several multiple reflections between bottom and surface. Fig. 18
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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectoceanbottom
