Validation of the [TAMU]² side-scan bathymetry compared to bathymetry along Shinkai 6500 tracks

Thierry Tonnerre, Ph.D.
Geological Survey of Japan

Wednesday, May 12, 1999
3:00 p.m.—Pacific Forum

Common bathymetric maps, with a resolution of c.a. 200 mX200 m at water depth of » 3,000 m are valuable for regional-scale interpretations, but provide only a general depth range for detailed studies at the submersible scale. [TAMU]² bathymetry provides a resolution of down to 12 mX12 m at water depth of » 3,000 m, which reveals fine topographic features at submersible scale. [TAMU]² bathymetry is compared to that determined along Shinkai 6,500 tracks (resolution of c.a. 0.1 mX0.1 m) in order to establish whether these features are real or not. Longitude, latitude, and depth shifts are taken into account since measurements occurred at different times under different navigation systems and bathymetry tools.

The comparison is carried out for two locations along the Southeast Pacific Rise axis: at 17º25'30"S, where the bathymetry is gentle and hummocky, and at 18º26'00"S, where it is rough with an axial trough. We compare the [TAMU]² bathymetry from the 1995 FAST Ridge expedition to that of the Shinkai 6500 along 15 dives of the RidgeFlux'97 expedition. For each computation, the shift maps of the correlation coefficients r² of the bisector slopes s and of d, defined as ((r²-1)²+(s-1)²)^0.5, enable us to select one exclusive best-fitted area. Most of the differences between the [TAMU]² and the Shinkai 6500 bathymetries are less than a few meters. The remaining differences can be interpreted as temporal changes occurring between the two cruises.

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