Sunda Trench an underwater ridge, and much of the trench is at least partially filled with sediments. Mappings after the 2004 Indian Ocean earthquake of the plate boundary showed resemblance to suspension bridge cables, with peaks and sags, indicative of asperity and locked faults, instead of the traditional wedge shape expected. Some of the earliest exploration of the Trench occurred in the late 1950s when Robert Fisher, Research Geologist at the Scripps Institution of Oceanography, investigated the trench as part of a worldwide scientific field exploration of the world's ocean floor and sub-oceanic crustal-structure. Bomb-sounding, echo-train analysis and manometer were some of
Japan Trench earthquakes within the deeper part of the plate interface zone. No earthquakes have been observed or reported from the shallow aseismic zone of the north Japan Trench. Regions of rough ocean bottom subduction are correlated with large normal faulting earthquakes within the outer-rise region, along with larger tsunami earthquakes occurring at the shallow region of the plate interface (megathrust events) . In 1980, lipids samples were taken via sediment cores located on both the landward and distal sides of the Japan Trench during six sections of the Deep Sea Drilling Project's transect. They were analyzed using gas chromatography and computerized-gas