Ocean-bottom reflectivity (a point of view)

Abstract

The analysis procedures for extracting bottom loss values from pulsed acoustic signals that have interacted with the ocean bottom do not inherently consider sub-bottom refraction and reflection of sound, which are important effects at low frequencies (i.e.; < 500 Hz). Sound returning from the sub-bottom can constructively interact with sound reflected from the water-sediment interface, yielding negative bottom loss results. To support this premise a Fast Field Program (FFP) time domain model simulation of a bottom loss measurement was performed in which the lateral wave was the only additional arrival interacting with the bottom reflected wave arrival. The simulation demonstrates a plausible cause for anomalous bottom loss results and suggests that propagation models must accommodate the environmental description of both the water column and ocean bottom.