Trans-dimensional geoacoustic inversion on a range-dependent track: Using chirp subbottom survey data as prior information for seabed layering

Geoacoustic inversion methods can be broadly divided into two categories. Fixed-dimensional methods are based on the assumption of a known environmental parametrization, including the number of seabed layers. Trans-dimensional (trans-D) methods estimate the environmental parametrization as part of the inverse problem. Although trans-D methods are very powerful, they have barely been applied in range-dependent geoacoustic inversion, and fully range-dependent trans-D inversion is a challenging problem. To mitigate this issue, we propose to use chirp subbottom survey data as prior information within a trans-D inversion method. To do so, the method considers the seabed as an unknown number of homogeneous sediment layers; the number of layers and geoacoustic properties within layers are constant over range, but layer interface depths are range dependent, with the lateral variation informed by the two-way travel-times to reflectors from the chirp survey. The method was successfully applied for single hydrophone geoacoustic inversion using data collected during the 2017 Seabed Characterization Experiment. [Work supported by the Office of Naval Research.]