The acoustic diversity of the seabed based on the similarity index computed from Chirp seismic data

The similarity index (SI), computed from the singular value decomposition of seabed-echo envelopes recorded in Chirp seismic data, was tested in mapping the acoustic diversity of the seabed in Suyong Bay, Busan, Korea. Rocky bottom is characterized by low SI values, indicating acoustic heterogeneity, and sedimentary seabed by high SI values, also indicating acoustic homogeneity. Isolated areas of low SI values, not identified as rocky bottom in Chirp profiles, may suggest a shallow basement. The gradual seaward change of the substratum from coarse-grained to relatively poorly sorted, finer-grained sediments also corresponds to an overall seaward decrease in the SI value. The straightforward and quick computation of the SI makes it possible to assess the gross acoustic diversity of the seabed in almost real time.