Acoustic Masking Due to Gases in Shallow Seismic Profiling on the Shelf Off Bombay

Abstract

Shallow seismic profiling on the inner shelf off Bombay indicates 25-35 m thick acoustically transparent clays covering the seabed. At depth of 22 to 30 m and 50 m the profiles and echograms are marked by turbidity resembling inverted U or mushroom like features which extend from the underlying reflector, i.e. sand and reach within 5-10 m of the surface. These features resemble the acoustic masking due to gases reported in shallow seismic profiles and echograms from estuaries and bays elsewhere. The gases may have originated due to the biogenic degradation of organic matter or seepage from greater depths because these occurrences lie in a basin with known oil and gas fields.