Marine reservoir correction for the Pacific coast of central Japan using C ages of marine mollusks uplifted during historical earthquakes

In this study we utilize marine shell samples from two levels of historically uplifted sessile mollusk assemblages and raised wave-cut benches to evaluate the marine reservoir correction (ΔR) for the Pacific coast of central Japan. Elevation measurements of the uplifted marine shells indicate that the lower assemblage emerged during the 1923 Taisho Kanto earthquake (M7.9), whereas uplift of the upper assemblage is most likely but less confidently ascribed to the 1703 Genroku Kanto earthquake (M8.2). Radiocarbon dating of carefully selected samples from the upper and lower assemblages yielded very similar ΔR values of 82 ± 33 and 77 ± 32 yr, respectively. We regard the former ΔR value as a representative and more reliable value given the uncertainty in correlation of the upper assemblage with the 1703 earthquake. This result is consistent with previously reported ΔR values for the Pacific coast of south-central Japan and areas around the Sea of Japan that are influenced by warm ocean currents. Radiocarbon dating of coseismically uplifted shells can aid in estimating marine reservoir ages in the tectonically active Japan Islands.     

Three‐dimensional microstructure of samples recovered from asteroid 25143 Itokawa: Comparison with LL5 and LL6 chondrite particles

In this study, the three‐dimensional (3‐D) microstructure of 48 Itokawa regolith particles was examined by synchrotron microtomography at SPring‐8 during the preliminary examination of Hayabusa samples. Moreover, the 3‐D microstructure of particles collected from two LL6 chondrites (Ensisheim and Kilabo meteorites) and an LL5 chondrite (Tuxtuac meteorite) was investigated by the same method for comparison. The modal abundances of minerals, especially olivine, bulk density, porosity, and grain size are similar in all samples, including voids and cracks. These results show that the Itokawa particles, which are surface materials from the S‐type asteroid Itokawa, are consistent with the LL chondrite materials in terms of not only elemental and isotopic composition of the minerals but also 3‐D microstructure. However, we could not determine whether the Itokawa particles are purely LL5, LL6, or a mixture of the two. No difference between the particles collected from Rooms A and B of the sample chamber, corresponding to the sampling sequence of the spacecraft's second and first touchdowns, respectively, was detected because of the statistically small amount of particles from Room B.     

Evolution and effect of the stress concentration and rock failure in the deep multi-seam coal mining

Supports crushing accident occasionally occurs in the protected seam exploitation of deep multi-seam coal mining structure and results in adverse effect to the production. To prevent its recurrence in a newly developed working field, a 3D numerical extraction model was built based on the geologic and mining conditions of Jining coal mine to evolve the changes, state and characteristics of the reconstructed vertical and lateral stress in rock interlayer after protective seam exploitation. Stress release and increase zones of this mining structure were separated. Mining-induced localized stress concentration and the interlayer rock failure behavior were explored. The action of concentrated stress on the hydraulic supports in protected seam was discussed upon the major stress redistribution. Using the infinitesimal strain method, a mechanical model was created to further explore, from the vertical and lateral directions, the cause and mechanism of localized stress concentration and rock failure behavior in rock interlayer. The field investigation was finally performed to verify the numerical and mechanical results, and the essential control measures were proposed to prevent this accident. Key findings of this study bring some new insights into the deep multi-seam coal extraction and help to promote a more reliable underground mining.     

Experimental and Numerical Investigations of Ground Deformation Using Chemical Grouting for Pipeline Foundation

Based on experimental and numerical investigations, the present paper focuses on under ground scope (UGS) chemical grouting method that can actually improve the pipeline surrounding foundation to solve pipeline saggy damage. According to the experimental results, a solution-type injection material could make lager soil deformation, using less total slurry amount than suspension-type injection material. Therefore, a suspension-type injection material with shorter gel time is more suitable for the UGS method, making it more effective to reinforce the pipeline foundation and restore pipelines. The results of some patterns of injection tests revealed relationship between the behavior of the grouting material and the deformation of the soil. It is found that the material can be injected into a foundation by fracture grouting if the permeation coefficient is lower than 1.00 × 10⁻³ mm/s. The situation was analyzed by using 2-D finite element method analysis software Phase2, and the analysis result proposes that the real data and simulation data are nearly the same in impermeable soil. Furthermore, even if the construction object is permeable soil, it can also be become impermeable soil by two phases grouting: soil improvement grouting and restoration grouting.     

Tsunami deposit associated with the 2011 Tohoku‐oki tsunami in the Hasunuma site of the Kujukuri coastal plain,Japan

We describe the detailed sedimentary characteristics of a tsunami deposit associated with the 2011 Tohoku‐oki tsunami in Hasunuma, a site on the Kujukuri coastal plain, Japan. The thick tsunami deposit was limited to within 350 m from the coastline whereas the inundation area extended about 1 km from the coastline. The tsunami deposit was sampled by excavation at 29 locations along three transects and studied using peels, soft‐X imaging and grain‐size analysis. The deposit covers the pre‐existing soil and reached a maximum measured thickness of 35 cm. It consists mainly of well‐sorted medium to fine sand. On the basis of sedimentary structures and changes in grain size, we divided the tsunami deposit into several sedimentary units, which may correspond to multiple inundation flows. The numbers of units and their sedimentary features vary among the three transects, despite the similar topography. This variation implies a considerable influence of local effects such as elevation, vegetation, microtopography, and distance from footpaths, on the tsunami‐related sedimentation.     

A petrological and geochemical study on time-series samples from Klyuchevskoy volcano,Kamchatka arc

To understand the generation and evolution of mafic magmas from Klyuchevskoy volcano in the Kamchatka arc, which is one of the most active arc volcanoes on Earth, a petrological and geochemical study was carried out on time-series samples from the volcano. The eruptive products show significant variations in their whole-rock compositions (52.0–55.5 wt.% SiO₂), and they have been divided into high-Mg basalts and high-Al andesites. In the high-Mg basalts, lower-K and higher-K primitive samples (>9 wt.% MgO) are present, and their petrological features indicate that they may represent primary or near-primary magmas. Slab-derived fluids that induced generation of the lower-K basaltic magmas were less enriched in melt component than those associated with the higher-K basaltic magmas, and the fluids are likely to have been released from the subducting slab at shallower levels for the lower-K basaltic magmas than for higher-K basaltic magmas. Analyses using multicomponent thermodynamics indicates that the lower-K primary magma was generated by ~13% melting of a source mantle with ~0.7 wt.% H₂O at 1245–1260?°C and ~1.9 GPa. During most of the evolution of the volcano, the lower-K basaltic magmas were dominant; the higher-K primitive magma first appeared in AD 1932. In AD 1937–1938, both the lower-K and higher-K primitive magmas erupted, which implies that the two types of primary magmas were present simultaneously and independently beneath the volcano. The higher-K basaltic magmas evolved progressively into high-Al andesite magmas in a magma chamber in the middle crust from AD 1932 to ~AD 1960. Since then, relatively primitive magma has been injected continuously into the magma chamber, which has resulted in the systematic increase of the MgO contents of erupted materials with ages from ~AD 1960 to present.     

Denaturing gradient gel electrophoresis shows that bacterial communities change with mid-ocean ballast water exchange

Ships carry ballast water for better stability and to control trim. However, the discharge of ballast water near ports is known to transport invasive species from one coastal area to another. The exchange of ballast water on the high seas is supposed to reduce such invasions of exotic species. In this study, we used denaturing gradient gel electrophoresis (DGGE) to analyze the composition of the bacterial community in ballast water before and after such a mid-ocean exchange, and we also measured total bacterial counts. Our findings confirmed that the ballast water was replaced by the mid-ocean exchange, as indicated by the marked change in the composition of the bacterial community. There was also a significant decrease in bacterial abundance after the mid-ocean exchange. Finally, our findings support the incubation hypothesis, because the composition of the bacterial communities changed over time within the same ballast water.     

Probabilistic assessment for seismic performance of port structures

Past experience has shown that ports are often susceptible to severe damage during earthquakes. From field damage data of 1995 Kobe earthquake, it is observed that the seismic behavior of port structures shows significant variability. In this study, a 2D numerical model, representing PC1 berth located in Port Island, Kobe and damaged in the 1995 Kobe earthquake, has been developed and used to simulate seismic behavior. It has been found that the uncertainties in the friction angle and the shear modulus of reclaimed soil contribute most to the variability of the residual horizontal displacement (RHD) response of the quay wall of port structures. To investigate the propagation of uncertainties of soil–structure system to the quay wall, a tornado diagram and a first-order second-moment analysis are used. Uncertainty of ground motions has also been investigated. Based on the results, design considerations have been provided.