The data presented stem from a suite of geotechnical experiments carried out on whole-round samples drilled during Ocean Drilling Program (ODP) Leg 186, West Pacific Seismic Network, Japan Trench. The scientific objectives of the cruise were the installation of two in situ measurement devices (seismometers, strainmeter, and tiltmeter) (for details see the Leg 186 Initial Reports volume [Sacks, Suyehiro, Acton, et al., 2000]) in the forearc of the Japan Trench at Sites 1150 and 1151. The measurements may help explain why there are seismic (Site 1150) and aseismic (Site 1151) domains in the forearc. Laboratory triaxial deformation tests on eight samples from different depths in the two drilled sections (see Table T1 should provide information on the static stress strain behavior of the sedimentary rocks of both sites.
Triaxial tests are a useful tool to determine deformation-specific properties of rocks under realistic conditions (i.e., a cylindrical specimen is subjected to a confining pressure comparable to the horizontal stress in the Earth's crust). Vertical stress resulting from lithostatic overload is simulated by axial piston loading. The vertical load is increased until failure occurs. From the possible types of triaxial tests, the consolidated undrained (CU) test is considered to be most suitable to simulate abrupt earthquake-induced deformation, a buildup of pore pressure, which results from impeded drainage in the clayey sediments and sedimentary rocks. In contrast, the consolidated drained (CD) test permits the escape of pore water without an increase of pore pressure. Deformation rates during CD tests are 10 times lower than those of CU tests.
Some samples were cut in several orientations to the artificially generated fault surface and were prepared for the scanning electron microscopy (SEM) to investigate the characteristics and development of the pore space with depth, as well as, the orientation and microstructures of the platy and clayey mineral components on the artificial fault plane surfaces.