Subsurface Exploration via Satellite: Structure Visible in Seasat Images of North Sea, Atlantic Continental Margin, and Australia

Abstract

Satellite observations of the sea-surface height are sensitive to crustal structure, overcoming the inability of previous remote-sensing techniques to penetrate the Earth's surface. Seasat gravity images have been compared with the structure of offshore sedimentary basins. In northwestern Europe, Seasat images display primary structural features (e.g., the Anglo-Dutch and smaller basins, down to the scale of the Manx-Furness basin), and numerous secondary structural features (e.g., the Halibut horst). Additionally, because of their synoptic viewpoint, Seasat images reveal features hard to distinguish. I cite as an example a basement ridge extending from Scotland to Norway, in position to have controlled marine circulation during deposition of the principal source rock, wh ch is equivalent to the Kimmeridge Clay. In North America and South America, Seasat images have been used to examine the relation of the Atlantic fracture zones to the structure of the continental margin of the United States and Brazil. In Australia, known basins of the northwest continental margin and the Bass Strait have been compared with Seasat projections of shallow structure. In comparison with reconnaissance seismic, magnetics, and ship-borne gravity surveys, Seasat images are valuable in discovering the presence of thick sediment accumulations; Seasat images are potentially more valuable than seismic and magnetics in the presence of basement masking by intrasectional volcanics or massive carbonates. In known basins, Seasat data deliver a uniform, synoptic view, permitting the identification of large structural features; in this form, these images give the structural geologist a tool like that given the stratigrapher by regional seismic sections. In remote unexplored regions, Seasat images provide a means of optimizing the layout of reflection seismic. The gravity data from Seasat offer the first of increasingly accurate structural images to be expected from altimetric satellites.