Mass flow deposit south of Central Andaman Trough, Andaman Sea: evidence from sub bottom profiler records

Abstract

A total of 2577 line-km sub bottom profiler data recorded over East Andaman Basin, Sewell and Mergui ridges, south of Central Andaman Trough, Andaman Sea, revealed distinctive echo types representing different seabed material and seafloor morphology. Echo Type I, Type-IIIA, Type-IIIB and Type IVA prevail over ridges, slopes of Sewell rise and Mergui ridge. Scarp head and slides (Types II, Type IVA) occur extensively over the entire slope areas of the ridges. Whereas in East Andaman Basin area, top sub bottom reflectors are almost flat in all transects and downward it becomes wavy, chaotic and hummocky in nature. This means that present day depositional environment is relatively calm as compared to bottom unit, which means the bottom most units is formed by the mass flow deposit. These evidences from echo pattern, shows a successive slope failure and supports frequent seismic shaking related to the rifting of Central Andaman Trough.