BURIED IMPACT CRATERS REVEALED BY FILTERING GRAVITY DATA

Earth’s dynamic geological processes have eroded or concealed most terrestrial impact craters. Because drilling is costly, geophysical measurements play an important role in mapping these buried structures. Bouguer gravity maps superimpose the effects of regional and local structures with the low-amplitude anomaly due to the impact feature. We investigated how variations in grid spacing, kind of numerical filter and filter dimensions affect residual anomaly maps. Where the regional gravity is relatively simple, a polynomial fit of selected stations beyond the influence of the crater best reveals the crater’s gravity signature. For large craters such as Kentland Dome and the Manson impact structure, downward continuation, curvature and Griffin ring filters generate contour maps showing much of the circular crater edge and central uplift. Manson appears to be a multi-ring complex crater, at least through about 250 degrees clockwise from north. High-pass numerical filters also magnify the noise present in every data set, noise that must be minimized by employing meticulous field technique and inspecting survey results during the field campaign, when suspicious stations can be reoccupied and vital data gaps recognized and filled.