A number of sand waves and mega-ripples are found on two submarine sand banks (Inosakinotsugai and a non-named bank eastward of Koyoshima) in Bisan Seto means of a side-scanning sonar (Bottom Sonar) and echo sounding.
Straight type sand waves developed on Inosakinotsugai and winding typed ones developed on the non-named bank. The former are arranged at right angles to the direction of the strongest tidal stream flowing over Inosakinotsugai. The latter show a composite pattern consisting of main sand waves having NW-SE trend formed by the strongest tidal stream flowing along the south wing of the bank and subsidiary sand waves having NNE-SSW trend generated by the strongest tidal stream flowing along the north wing of the bank.
On the other hand, those banks have areas of mega-ripples independ of the areas of sand waves, though both areas are overlapping at their boundaries. Mega-ripple areas cor respond to the area of granule and gravel, and sand wave areas correspond to the area of coarse and medium sand.
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