A high resolution bathymetry survey reveals the detailed morphology of the Southern Mariana Trench. Distinct right stepping, N80｡E trending en echelon deeps were found on the trench bottom within the Challenger Deep. Horst and graben structures were revealed on the outer swell of the Southern Mariana Trench. These structures, as well as slope-failure on the inner and outer slopes of the trench are similar to features observed in other deep sea trenches. We propose here that the Southern Mariana Trench is a transform fault based on swath mapping, morphological analysis and tectonic interpretation. The en echelon deeps formed in a right-lateral strike-slip stress regime related to oblique Pacific/Caroline Plate subduction under the Southern Mariana Trench combined with the Mariana Trough backarc spreading. We confirm that the worldﾕs deepest point lies iin the western portion of the Challenger Deep, among the en echelon deeps.