A DETAILED GRAVITY-FIELD OVER THE REYKJANES RIDGE FROM SEASAT, GEOSAT, ERS-1 AND TOPEX/POSEIDON ALTIMETRY AND SHIP-BORNE GRAVITY

The method of least-squares collocation (LSC) was used to construct a detailed gravity field over the Reykjanes Ridge using Seasat, Geosat, ERS-1, TOPEX/POSEIDON altimeter data and shipborne gravity data. Mean altimeter-derived geoid gradients, along with their standard deviations, were used in order to avoid cross-over adjustment of sea surface heights. The ship data were adjusted to a satellite-only gravity field using a quadratic polynomial in time. and then merged with the satellite data, to produce a combined gravity field. The necessary covariance functions were derived using the law of covariance propagation. In a test case, a comparison between a combined gravity field and ship data not included in the calculation yielded an rms difference of 2.31 mgals. The combined gravity field contains a wealth of short-wave length information and clearly reveals the detailed tectonic structures associated with the Reykjanes Ridge.