Consolidation properties, stress history, and modeling of pore pressures for deep sea sediments at the Nankai Trough

Consolidation tests typically performed by geotechnical engineers can be modified to achieve the research goals of geologists interested in the behavior of sediments at subduction zones. Subduction zones are of interest to geologists because they are locations where earthquakes are likely to occur. By researching the behavior of the sediments at subduction zones, geologists hope to better understand the physical and chemical changes in the sediment due to the subduction process.; A consolidation-testing program was carried out on samples from the Nankai Trough subduction zone off the southeast coast of Japan. Seventeen consolidation tests were performed on samples from the Nankai Trough, five tests on samples cored from reference Site 1173 on the Muroto Transect and twelve tests on samples cored from reference Site 1177 on the Ashizuri Transect. Engineering properties calculated for each sample include the consolidation properties of the sediment, the maximum past pressure (sigma' v), and the hydraulic conductivity (k).; Void ratio-effective stress relations were also developed for the sediments at both Site 1173 and Site 1177. These relations were used to model pore pressures in the sediment column at both sites. The pore pressure model for Site 1173 indicates high pore pressures in the vicinity of the decollement. The pore pressure model for Site 1177 indicates high pore pressures in the vicinity of sand packets that are sealed in three dimensions, and possible high pore pressures in the vicinity of the depth where the decollement is expected to pass through the site.