Mapping the occurrence of gas in subsurface marine sediment: A comparison of acoustic methods

The submarine geophysical methods research are indirect methods, but the result in seafloor and subsurface sea characterization is very confident. The acoustic classification of sediments has been increasingly studied in order to help, facilitate and optimize the definition of the characteristics of the sediments present in the bottom and subsurface sea. The classifiers sediment, software developed to assist in the seafloor characterization, using several algorithms, select the most representative according to the study area to generate classification maps. It is critical that the factors used during acquisition to be known and maintained. This is an important factor for any geophysical survey. The presence of gas in subsurface sediments near the sea surface is known in Guanabara Bay, Rio de Janeiro and Conceição Lagoon, Florianópolis, Santa Catarina. These two areas were used to compare the geophysical subbottom acoustic profile and single beam classification sediments. SBP data were acquired in frequency between 1 and 6 kHz, high resolution, and single beam data were acquired at frequencies of 50 and 200 kHz. Comparison data was performed taking into account the frequency of the data, number of classes, gas areas and depth of occurrence gas in the subsurface. The sediment subsurface characterization to identifying gas areas using single beam data is most effective with frequency of 50 kHz than 200 kHz.