Evaluation of Ferromanganese Crusts on Western Pacific Seamounts Using a Distance–Relative Water Depth Variogram Model Based on Multiseamount Data

High survey costs restrict geological stations to an extremely sparse distribution, which has constrained the establishment of geostatistical models of ferromanganese crust thickness on individual seamounts. Moreover, because crust thickness is independent of direction yet controlled by water depth, the traditional “distance–direction” variogram cannot adequately describe its spatial autocorrelation. To address these limitations, data from additional seamounts were incorporated, and new model functions were introduced based on previous work to further refine the multiseamount “distance–relative water depth” variogram model. First, ferromanganese crust thickness data from five seamounts in the western Pacific Ocean were transformed into a combined dataset with identical means and similar variances. Second, point-pair searches constrained by relative water depth (e.g., 200-m intervals) were performed on this dataset to obtain experimental variogram values for the “distance–relative water depth” model. Third, guided by the form of the two-dimensional experimental variogram scatter plot, spherical and sine functions were fitted separately, yielding two variograms. Finally, both were applied to Kriging spatial interpolation of crust thickness on the Dacheng Seamount. The results show that both variograms outperform traditional interpolation methods, with the sine model variogram performing best. The variogram derived from the five-seamount combined data closely resembles the one previously obtained from four seamounts, indicating that variograms fitted from multiseamount combined data are reasonably robust. This approach therefore offers an effective option for interpolating ferromanganese crust thickness on data-sparse seamounts such as the Dacheng Seamount.