The renavigation of Sea Beam bathymetric data between 9° N and 10° N on the East Pacific Rise |
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| Authors: | W S D Wilcock D R Toomey G M Purdy S C Solomon |
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| Institution: | (1) MIT/WHOI Joint Program in Oceanography, Massachusetts Institute of Technology, Bldg. 54-510, 02139 Cambridge, MA, USA;(2) Department of Geological Sciences, University of Oregon, 97403 Eugene, OR, USA;(3) Department of Geology and Geophysics, Woods Hole Oceanographic Institution, 02543 Woods Hole, MA, USA;(4) Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 02139 Cambridge, MA, USA;(5) Present address: Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego, 92093 La Jolla, CA, USA |
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| Abstract: | We present a gridded Sea Beam bathymetric map of a 5100 km2 area between 9° and 10° N on the East Pacific Rise (included as a color separate accompanying this issue). The raw bathymetric data are renavigated using a technique for calculating smooth adjustments to navigation that incorporates absolute constraints from satellite fixes and acoustically-located explosive shots, and relative constraints from the misfit of bathymetric data at ship track crossovers. We describe a back-projection technique for gridding the bathymetric data that incorporates an approximation for the power distribution within a narrow-beam echo sounding system and accounts for the variable uncertainties associated with multi-beam data. The nodal separation of the resulting map is ~ 80 m in both latitude and longitude, and the sampling of grid points within a 60 × 85 km2 region is in excess of 99%. A formal analysis of variance is applied to the gridded bathymetric data. For each grid point, the difference between the variance of data from within a track versus data from between tracks provides an upper bound on the magnitude of bathymetric misfits arising from navigational errors. The renavigation results in an 88% reduction in this quantity. We also examine the effects of renavigation on the misfit of magnetic and gravity data at crossovers and compare our results with other bathymetric surveys. A striking feature of the final bathymetric map is the sinuous regional shape of the rise axis. In plan view, the local trend of morphology sometimes varies by up to 15° and the distances separating changes in morphological trend are about 10–20 km. In cross section the slopes of the rise flanks are notably asymmetric and show some correlation with the offset of the axial magmatic system as detected by seismic methods. |
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| Keywords: | Sea Beam bathymetry renavigation gridded map East Pacific Rise |
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