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Alaska Bathymetry: Central Gulf of Alaska Geological Features(pg 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

Geological Features of Central Gulf of Alaska

Middleton Island Submerged Marine Terraces

The discovery of the Middleton Island submerged marine terraces, which were not previously imaged, proves the benefit of carefully editing and plotting the bathymetry data. A) The unedited bathymetry, uncorrected for digitization and datum errors, is a mixture of pre- and post-1964 earthquake soundings, which produces numerous confusing artifacts. B) The edited, post-quake bathymetry produces a much cleaner surface, even though it uses fewer soundings, revealing submerged marine terraces, which generally lie parallel to the island's coastline. These are the relic marine terraces (George Plafker, Scientist Emeritus, US Geological Survey,personal communication, 2012), perhaps 20 of them, similar in size and orientation to those on the island described by Plafker and Rubin (1978) .

Mouse over image for unedited (A) and edited (B) Middleton bathymetry.

middleton

References
Plafker, G. and M. Rubin. 1978. Uplift history and earthquake recurrence as deduced from marine terraces on Middleton Island, Alaska, in Proceedings of Conference VI, Methodology for identifying seismic gaps and soon-to-break gaps: U.S. Geological Survey Open-File Report 78-943, p. 687-721.

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