Bathymetry computation from r‐ee‐air anomaly data

Abstract

It is well known that there is a certain amount of correlation between the gravity observations obtained at sea and the seafloor topography. It is also known that short‐wavelength bathymetry produces the short‐wavelength gravity anomalies, while the long‐wavelength bathymetry is compensated. The relationship between the gravity field and the seafloor topography is usually analyzed using a linear transfer function, called admittance. Admittance can be computed easily in the wave number domain from bathymetry and gravity spectra.

This article investigates the feasibility of bathymetry computation from free‐air anomaly data obtained from shipboard gravity data. We derive an objective function from theoretical admittance formulas and seek the minimum of that function in the solution space for unknown bathymetry by an exhaustive search method.

We apply this inversion technique to data collected south of the island of Hawaii by the Scripps Institution of Oceanography using the R/V T. Washington in 1987. Sea Beam was used to measure the bathymetry, and a Bell Aerospace BGM‐3 meter was used to measure gravity. The results show an error of less than 1% of depth, which is within the acceptable error range according to International Hydrographic Bureau standards.

Keywords:

• admittance
• bathymetry
• free‐air anomaly
• inversion