Improved Interpretation of Marine Sedimentary Environments Using Multi-Frequency Multibeam Backscatter Data
Backscatter mosaics based on a multi-frequency multibeam echosounder survey in the continental shelf setting of the North Sea were compared. The uncalibrated backscatter data were recorded with frequencies of 200, 400 and 600 kHz. The results showed that the seaﬂoor appears mostly featureless in acoustic backscatter mosaics derived from 600 kHz data. The same area surveyed with 200 kHz reveals numerous backscatter anomalies with diameters of 10–70 m deviating between −2 dB and +4 dB from the background sediment. Backscatter anomalies were further subdivided based on their frequency-speciﬁc texture and were attributed to bioturbation within the sediment and the presence of polychaetes on the seaﬂoor. While low frequencies show the highest overall contrast between different seaﬂoor types, a consideration of all frequencies permits an improved interpretation of subtle seaﬂoor features.