An existing model of seafloor backscattering [D. R. Jackson, D. P. Winebrenner, and A. Ishimaru, J. Acoust. Soc. Am. 79, 1410–1422 (1986)] was implemented with the additions of volume scattering from a random inhomogeneous continuum and scattering from subbottom interfaces. Results of computer simulations with the extended model were compared with values of scattering strength obtained from processed GLORIA data from the Monterey Fan off the coast of California. Regions of well-delineated high and low backscatter are seen in the GLORIA imagery. The geoacoustic input parameters for the simulation runs were either taken directly from or estimated from core data obtained by ground truth sampling in the image area. From the model simulation results it appears that the main factor causing the observed dichotomous character of the strength of returns in the Fingers Area is the presence or absence of a topmost, inhomogeneous silt-clay layer (with a thickness of around 1–1.5 m). In the high backscatter areas, inhomogeneous continuum volume scattering from the silt-clay layer predominates. In the low backscatter areas interface scattering from an acoustically hard, shallow subbottom sand interface (0–10 cm below the water–sediment interface) predominates. These two additions to the scattering model allow use of the ground truth measurements to constrain the input parameter values.
