Sediment Stripping Correction to Marine Gravity Data

Abstract

The knowledge of the bedrock topography (instead of the ocean-floor relief) is required in various geoscience studies investigating the evolution and structure of the oceanic lithosphere. The gross density structure and thickness of marine sediments were obtained from ocean drilling data or seismic surveys. Alternatively, marine gravity data corrected for the ocean and sediment density contrasts can be used for a detailed mapping of the bedrock topography. In this study, we compute and apply the sediment stripping correction to marine gravity data. The sediment density distribution is approximated by a 3-D density model derived based on the analysis of density samples from the Deep Sea Drilling Project. Methods for a spherical harmonic analysis and synthesis are utilized in computing the sediment stripping correction. Results show that this correction varies between 0 and 32 mGal. We also demonstrate that the approximation of heterogeneous sediment structures by a uniform density model yields large errors. The spectral analysis reveals a high correlation (>0.75) between the sediment-stripped marine gravity data and the bedrock topography. The application of the sediment stripping correction to marine gravity data enhanced the gravitational signature of the sediment-bedrock interface.