Description and classification of seafloor terrains using two-dimensional spectra models of bathymetry.

Abstract

A two-dimensional spectral model of bathymetry developed by Fox and Hayes [Rev. Geophys. 23(1), 1–48 (1985)] is applied to gridded sea beam data from the central Juan de Fuca Ridge in the northeast Pacific Ocean. Parameters of the model corresponding to (1) isotropic (nondirectionally dependent) roughness, (2) anisotropic (directionally dependent) roughness, (3) orientation of the anisotropic component, and (4) spectral rolloff (∼fractal dimension) are derived by fitting the model surface to two-dimensional amplitude spectra of bathymetry determined on a regular grid over the study area. Each term of the model is individually mapped and compared to ground truth data from SeaMARC-I sidescan sonar imagery. Parameters of the model clearly define the contrast between constructional volcanic terrain (rough, isotropic, with high fractal dimension) and tectonic extensional terrain (smoother, anisotropic, with low fractal dimension). An agglomerative, hierarchical cluster analysis is applied to the data, independent of spatial information, to delineate groups of spectra with similar characteristics. Distinct, mappable regions, corresponding to volcanic and tectonic provinces, are objectively determined. Also, coherent subregions of consistent spectral properties occur within the larger volcanic/tectonic divisions. The classification of large data sets, such as the entire Juan de Fuca Ridge system, can best be accomplished through the use of apriori techniques, such as k-means clustering, which requires the input of predefined characteristics for bathymetric provinces.