Geoacoustic models for bottom loss predictions

Abstract

A useful theoretical measure of acoustic interaction with the seafloor is the plane wave reflection coefficient (R) which is commonly expressed as bottom loss (20 log |R |)). Predictions modeling the seafloor as a sediment layer over a half‐space indicate that bottom loss should be proportional to frequency. Bottom loss measurements (50–1600 Hz) in the deep ocean, however, frequently show a loss that is inversely proportional to frequency. The locations of these anomalous sites are remarkably consistent with the boundaries of the Abyssal Plains which are characterized by turbidite layering. Geoacoustic models including the turbidite layers were constructed based on core data and a ray‐based acoustic model was employed to compare the model predictions with measured data in Abyssal Plain areas. The turbidite layering was modeled as a series of pelagic and terrigenous layers in a simple repeating sequence. Model predictions were in accordance with the measured data.