Disorder and damage of base‐isolated medical facilities when subjected to near‐fault and long‐period ground motions

A series of full‐scale shaking table tests were conducted at E‐Defense for a four‐story base‐isolated hospital. The operation room in the specimen was chosen for detailed examination of its disorder and damage during large ground motions. It was arranged with various medical appliances in as a realistic manner as possible, and the appliances were characterized by casters installed at the bottom to ensure mobility. Two types of ground motion, the near‐fault ground motion and long‐period ground motion, were adopted, and the responses of the appliances were recorded using the motion capture technique. Thanks to the base isolation, the floor response was greatly reduced, and no disorder or damage was observed in the operation room except for the case when subjected to a long‐period ground motion. In this case, the unlocked appliances moved seriously (by more than 3 m), and collisions occurred between the appliances and between appliances and the surrounding wall. The force of collision reached 36 kN, which is sufficient to injure a person. The acceleration due to collision was as high as 10 g, which is far beyond what can be tolerated by acceleration‐sensitive appliances. It is notable that such large motion was not observed once the appliances were locked. The test was also carried out for the corresponding fixed‐base structure. Among all cases in the experiment, by far the most serious damage occurred in the fixed‐base structure when subjected to the near‐fault ground motion, clearly because the floor response was significantly amplified from the ground motion. Copyright © 2014 John Wiley & Sons, Ltd.     

Microbially induced formation of ooid-like coated grains in the Late Cretaceous methane-seep deposits of the Nakagawa area, Hokkaido, northern Japan

Abstract   Ooid-like coated grains are found in the Late Cretaceous methane-seep deposits in the Nakagawa area, Hokkaido, Japan. The coated grains were examined using macro- and microscopic observations, electron-probe microanalysis, and biomarker analysis. They are round- to oval-shaped, with nuclei consisting of fractured sediment and micritic envelopes. The fractures probably occurred as a result of increasing hydrostatic pressure when the sediment was still unconsolidated or weakly consolidated. Biomarker analysis revealed that two types of molecules, crocetane and PMI, are predominant in the hydrocarbon fraction with highly negative carbon isotopic composition as low as −122‰ ( vs Vienna Peedee Belemnite). These data suggest that the coated grains were formed under the influence of anaerobic oxidation of methane, near the sediment/seawater interface. The presence of such grains indicates that methane-containing pore water reached the sea floor at that time.     

Collapse simulation of a four‐story steel moment frame by a distributed online hybrid test

The collapse of a one‐bay, four‐story steel moment frame is simulated in this study by the proposed peer‐to‐peer (P2P) Internet online hybrid test system. The typical beam hinging mechanism, which is ensured by a strong‐column, weak‐beam design, is reproduced. The plastic hinges at the column bases are taken as the experimental portions, while the superstructure is analyzed numerically by a general‐purpose finite element program. The implicit plastic rotations of the two column bases are treated as boundary displacements. In order to account for the complex behavior of the column bases, the P2P system is modified to use the secant stiffness during iterations, and the physical specimens are designed such that the plastic hinge behavior can be obtained. For this study, the three substructures are distributed to different locations. A large ground motion is repeatedly imposed until the column bases lose their capacity to sustain the gravity load. As a result, significant deterioration is observed at both column bases. The proposed P2P system is thus demonstrated to be able to accommodate multiple‐tested substructures involving unstable behavior. The results suggest that the P2P Internet online hybrid test system provides a reliable means of studying structures up to collapse. Copyright © 2008 John Wiley & Sons, Ltd.     

Color measurements of volcanic ash deposits from three different styles of summit activity at Sakurajima volcano,Japan: Conduit processes recorded in color of volcanic ash

We measured quantitatively colors of volcanic ash deposits erupted from three different styles of summit activity (Strombolian activity, Vulcanian explosions and continuous ash venting activity) at Sakurajima volcano from 1974 to 1985. Colors of Strombolian ash samples have larger yellow components of their visible spectra (b^? values) than those of explosion and continuous venting ash samples. Colors of explosion ash samples show larger variation in both red and yellow components of their visible spectra (a^? and b^? values, respectively), while colors of continuous venting ash samples are in the narrow ranges within colors of explosion ash samples. Colors of components with lower densities than 3.1 g/cm³ (groundmass and phenocrystic plagioclase) obtained by magnetic and heavy liquid separation methods are similar to the unseparated bulk ash samples. This result suggests that the color variations of ash deposits are mainly originated from the particles composed of groundmass. The particles can be classified into three different types of particles with different vesicularity and crystallinity (vesicular particle [VP], dense particle with vesicles [DPV] and dense particle without vesicles [DP]). Analytical results of component proportions, chemical compositions of groundmass glasses, ferrous iron contents and surface ferric materials show that (1) VP has larger yellow components of the visible spectrum (b^? values) and high ferrous iron content, and is less crystallized than the DP and DPV, (2) DP has larger red and yellow components of its visible spectrum (a^? and b^? values, respectively) and involves ferric materials on the surfaces produced by oxidation process, and (3) DPV has smaller red and yellow components of its visible spectrum (a^? and b^? values, respectively) and involves less ferric materials on the ash surfaces. Color differences of ash deposits from three different activity styles can be explained by the different mixing ratios of VP, DPV and DP. During the Strombolian activity, the VP is a main component in the ash, which is formed from relatively less degassed and crystallized magma. In the Vulcanian explosion and continuous ash venting activity, the proportions of DPV and DP in ash are larger than that in the Strombolian activity. The highly crystallized DP may correspond to a vent cap, and DPV to a magma below the cap. The color measurements of ash deposits provide information on the pre-eruptive processes at the shallower levels of a conduit.     

A new type of orthopyroxenite xenolith from Takashima, Southwest Japan: silica enrichment of the mantle by evolved alkali basalt

We found fine-grained Fe-rich orthopyroxene-rich xenoliths (mainly orthopyroxenite) containing partially digested dunite fragments of Group I from Takashima, Southwest Japan. Orthopyroxenite veinlets, some of which contain plagioclase at the center, also replace olivine in dunite and wehrlite xenoliths of Group I. This shows high reactivity with respect to olivine of the melt involved in orthopyroxenite formation, indicating its high SiO₂ activity. The secondary orthopyroxene of this type is characterized by low Mg# [= Mg/(Mg + total Fe) atomic ratio] (down to 0.73) and high Al₂O₃ contents (5–6 wt%). It is different in chemistry from other secondary orthopyroxenes found in peridotite xenoliths derived from the mantle wedge. Clinopyroxenes in the Fe-rich orthopyroxenite show a convex-upward REE pattern with a crest around Sm. This pattern is strikingly similar to that of clinopyroxenes of Group II pyroxenite xenoliths and of phenocrystal and xenocrystal clinopyroxenes, indicating involvement of similar alkali basaltic melts. The Fe-rich orthopyroxenite xenoliths from Takashima formed by reaction between evolved alkali basalt melt and mantle olivine; alkali basalt initially slightly undersaturated in silica might have evolved to silica-oversaturated compositions by fractional crystallization at high-pressure conditions. The Fe-rich orthopyroxenites occur as dikes within the uppermost mantle composed of dunite and wehrlite overlying pockets of Group II pyroxenites. The orthopyroxene-rich pyroxenites of this type are possibly common in the uppermost mantle beneath continental rift zones where alkali basalt magmas have been prevalent.     

Oxygen isotope thermometry using quartz inclusions in garnet

Oxygen isotope ratios of quartz inclusions (QI) within garnet from granulite and amphibolite facies gneisses in the Adirondack Mountains, NY were analysed and used to determine metamorphic temperatures. Primary QI for eight of 12 samples have δ¹⁸O values significantly lower than matrix quartz (MQ). The primary QI retain δ¹⁸O values representative of thermal conditions during garnet crystallization, whereas the δ¹⁸O values of MQ were raised by diffusive exchange with other matrix minerals (e.g. mica and feldspar) during cooling. The δ¹⁸O differences between QI and MQ show that garnet (a mineral with slow diffusion of oxygen) can armour QI from isotopic exchange with surrounding matrix, even during slow cooling. These differences between δ¹⁸O in MQ and QI can further be used to test cooling rates by Fast Grain Boundary diffusion modelling. Criteria for identifying QI that preserve primary compositions and are suitable for thermometry were developed based on comparative tests. Relations between δ¹⁸O and inclusion size, distance of inclusion to host–garnet rim, core–rim zonation of individual inclusions, and presence or absence of petrological features (healed cracks in QI, inclusions in contact with garnet cracks lined by secondary minerals, and secondary minerals along the inclusion grain boundary) were investigated. In this study, 61% of QI preserve primary δ¹⁸O and 39% were associated with features that were linked to reset δ¹⁸O values. If δ¹⁸O in garnet is homogeneous and inclusions are removed, laser‐fluorination δ¹⁸O values of bulk garnet are more precise, more accurate, and best for thermometry. Intragrain δ¹⁸O(Grt) profiles measured in situ by ion microprobe show no δ¹⁸O zonation. Almandine–rich garnet (Alm_60–75) from each sample was measured by laser‐fluorination mass‐spectrometry (LF‐MS) for δ¹⁸O and compared with ion microprobe measurements of δ¹⁸O in QI for thermometry. The Δ¹⁸O(Qz–Grt) values for Adirondack samples range from 2.66 to 3.24‰, corresponding to temperatures of 640–740 °C (A[Qz–Alm] = 2.71). Out of 12 samples that were used for thermometry, nine are consistent with previous estimates of peak temperature (625–800 °C) based on petrological and carbon–isotope thermometry for regional granulite and upper amphibolite facies metamorphism. The three samples that disagree with independent thermometry for peak metamorphism are from the anorthosite–mangerite–charnockite–granite suite in the central Adirondacks and yield temperatures of 640–665 °C, ~100 °C lower than previous estimates. These low temperatures could be interpreted as thermal conditions during late (post‐peak) crystallization of garnet on the retrograde path.     

Sulfur bacteria originating from the water and organisms in a hydrothermally active area of the mid-okinawa trough

Hydrothermal venting and associated fauna were observed in the mid-Okinawa Trough during deep-sea diving byShinkai 2000. Water and organisms were collected there for on-board cultivation of sulfur bacteria. Sulfur bacteria capable of growing on an inorganic medium containing thiosulfate were subcultured and isolated. The isolated chemoautotrophic sulfur bacteria were all rod- to beanshaped, nonsporing, and gram-negative. They could also grow on an organic medium and thus were shown to be facultative chemoautotrophs. Their facultative chemoautotrophy would result in synergetic metabolism of both inorganic and organic substrates; thus the sulfur bacteria could be highly adaptive to nutritional diversity of hydrothermal vent areas.     

Vertical distribution of bacterial abundance in the northwest pacific ocean

Mixed populations of free-living marine bacteria were collected at depths from the surface to the bottom (1,960m in Suruga Bay and 1,585 m in the Japan Sea) in the northwest Pacific during deep-sea diving by the submersible,Shinkai 2000. Their abundance in total cell counts and in lipopolysaccharide (LPS) concentration was found to decrease with increasing depth, and the decreasing profiles were shown to be linear on logarithmic scales. The total cell counts and the LPS concentration showed a linear relationship on arithmetic scales, and the LPS content per cell was found to be 1.02×10^–14 g.     

Hydration of rhyolitic glass during weathering as characterized by IR microspectroscopy

The mechanism and rate of hydration of rhyolitic glass during weathering were studied. Doubly polished thin sections of two rhyolites with different duration of weathering (Ohsawa lava: 26,000 yr, Awanomikoto lava: 52,000 yr) were prepared. Optical microscope observation showed that altered layers had developed along the glass surfaces. IR spectral line profile analysis was conducted on the glass sections from the surface to the interior for a length of 250 μm and the contents of molecular H₂O (H₂O_m), OH species (OH) and total water (H₂O_t) were determined. The diffusion profile of H₂O_m in Ohsawa lava extends beyond the layer observed by optical microscope. The content of H₂O_m in the hydrated region is much higher than that of OH species. Thus, the reaction from H₂O_m to OH appears to be little and H₂O_m is the dominant water species moving into the glass during weathering. Based on the concentration profiles, the diffusion coefficients of H₂O_m(D_H2Om) and H₂O_t(D_H2Ot) were determined to be 2.8 × 10⁻¹⁰ and 3.4 × 10⁻¹⁰ μm² s⁻¹ for Ohsawa lava, and 5.2 × 10⁻¹¹ and 4.1 × 10⁻¹¹ μm² s⁻¹ for Awanomikoto lava, respectively. The obtained D_H2Om during weathering are more than 2-3 orders of magnitude larger than the diffusion coefficient at ∼20 °C that is extrapolated from the diffusivity data for >400 °C. This might suggest that the mechanism of water transport is different at weathering conditions and >400 °C.