Vertical variations in ²¹⁰Pb, ¹³⁴Cs, and ¹³⁷Cs content (Bq/kg) were measured in the uppermost 2 m of the INW2012 sediment core, which was taken from Lake Inawashiro-ko. Analyses of ²¹⁰Pb_(ex) suggest that the top 39 cm were deposited within the last 90 years, while ¹³⁴Cs and ¹³⁷Cs results indicate that a depth of 29 cm corresponds to the beginning of the 1950s. Combined with lithostratigraphic observations, these dates suggest that the massive sandy silt layer observed in the top 13.5 cm of the core was deposited as a result of the 2011 earthquake in the Pacific Ocean off the coast of Tohoku. In addition, the gray-brown clay layer between 42 and 37.5 cm depth is associated with the Mt. Bandai eruption in AD 1888. On the basis of these event horizons and their ages, sedimentation rates are estimated to be 1.0 and 2.0 mm/yr at depths of 200-42 cm and 37.5-13.5 cm, respectively.

A transect resistivity model was generated to a depth of 1.5 km around the Gomura Fault by conducting an audio-frequency magnetotelluric survey. The model clearly presents the structure of fault ruptures, and is characterized by three conductive regions and one moderately conductive region. One of the conductive zones and the moderately conductive zone are sub-horizontal and situated on the eastern side of the Gomura Fault; the former is shallow, whereas the latter is deep.

The resistivity structure of these layers and the surrounding area are well consistent both with their lithofacies and a resistivity log made to a depth of 1300 m near the survey line of this study. Pore water at the boundary between the weathered and weakly-weathered granitic rocks, combined with an increase in clay minerals, decreases the resistivity of the shallowest conductive layer. The second and third conductive regions are located beneath the surface traces of the Gomura and Go-seihou Faults, respectively. The second conductive region is interpreted as a fracture zone produced by fault movements, with a high water content and probably containing clay minerals. The observation that the third region is small and isolated may indicate that the Go-seihou Fault is a subsidiary fault. A comparison of the conductive fracture regions of the Gomura Fault and the Hijima Fault of the Yamasaki fault system suggest that the width and conductivity of a conductive region beneath the surface trace of an active fault are controlled by the mean slip rate and cumulative displacement, rather than the difference of ~1000 years since their most recent earthquake events.

Okushiri Island, located in southwest Hokkaido, Japan, was hit by an earthquake-generated tsunami in July 1993. An excavation survey revealed several event sand beds, interbedded with peaty sediments, in the lowland at the southernmost part of the island. These beds consist of relatively well-sorted fine- to medium-grained sand similar to sandy shoreline deposits; they are normally graded, fining and thinning landwards. Some beds show partial erosional bases and ripple cross-laminations, implying landward-directed paleocurrents, and grain fabrics also indicate the landward dispersal of clastics. The sand beds yield marine organic-walled microfossils such as dinoflagellate cysts and foraminiferal linings. These findings indicate that the sand beds are of tsunami origin. The results of carbon-14 dating and tephrochronology indicate that at least six tsunami events, including the AD 1741 Oshima-Ohshima and the AD 1993 Hokkaido Nansei-Oki tsunamis, have hit the island over the past 3000-4000 years.

To investigate the effects of confining pressure and pore water pressure on the strain behavior and deformation properties of Aji granite, triaxial compression tests were performed at a constant strain rate (5.0×10^－6 s^－1) under confining and pore water pressures of 10-40 MPa and 10-30 MPa, respectively. During the tests, axial and radial strains were measured by two biaxial strain gauges. The results revealed increases in maximum differential stress and onset of dilatancy with effective confining pressure. Young's modulus tended to increase with confining pressure and decrease with pore water pressure. However, Poisson's ratio remained nearly constant under these experimental conditions. Dilatancy is related to the formation of micro-cracks during deformation and is enhanced at low confining pressures under dry conditions. In contrast, it tends to be suppressed at a high pore water pressure (low effective confining pressure) under wet conditions. These results indicate that stress concentration at the crack tip can be relaxed by the presence of pore water. Moreover, water injection into the specimen during wet experiments rapidly increases at a stress level of ~96% maximum differential stress. This rapid increase can be attributed to the formation of a micro-crack network.

Black-colored rocks (Black-colored Rocks hereafter) occur as veins and a volcanic dike in the Tetori Group, southern Ishikawa Prefecture. The Black-colored Rocks are composed of angular lithic clasts in a fine-grained (<10-50 µm) matrix. The lithic clasts in veins are derived from the Tetori Group (mudstone, sandstone, and conglomerate), whereas those in the volcanic dike are derived from both the volcanic dike and the Tetori Group. The matrix of the Black-colored Rocks consists mainly of very fine-grained quartz (usually 10 µm in size) with minor amounts of feldspar, maghemite, and unidentified carbon-bearing fine-grains. The Black-colored Rocks contain abundant SiO2 relative to the host rocks. The chondrite-normalized rare earth element (REE) pattern of the Black-colored Rocks is similar to that of their host rocks, although the REE abundance is lower in the former.