A5063457999- Geological and Geochemical Analysis
- Geology and Paleoclimatology Research
- Methane Hydrates and Related Phenomena
- earthquake and tectonic studies
- Astro and Planetary Science
- Isotope Analysis in Ecology
- High-pressure geophysics and materials
- Paleontology and Stratigraphy of Fossils
- Hydrocarbon exploration and reservoir analysis
- Geochemistry and Geologic Mapping
- Planetary Science and Exploration
- Geochemistry and Elemental Analysis
- Nuclear Physics and Applications
- Groundwater and Isotope Geochemistry
- Earthquake Detection and Analysis
- Atmospheric and Environmental Gas Dynamics
- Arctic and Antarctic ice dynamics
- Geological and Geophysical Studies
- Radioactive element chemistry and processing
- CO2 Sequestration and Geologic Interactions
- Geological Studies and Exploration
- Seismology and Earthquake Studies
- Atomic and Subatomic Physics Research
- Ion-surface interactions and analysis
- Marine Bivalve and Aquaculture Studies
The University of Tokyo
2015-2024
The Open University of Japan
2018-2024
Sphere Institute
2012-2023
Tokyo University of Marine Science and Technology
2005-2010
Nitobe Memorial Nakano General Hospital
2009
Hiroshima University
1995-2002
Planetary Systems (United States)
1995-2002
Radon concentration in ground water increased for several months before the 1995 southern Hyogo Prefecture (Kobe) earthquake on 17 January 1995. From late October 1994, beginning of observation, to end December radon about fourfold. On 8 January, 9 days earthquake, reached a peak more than 10 times that at starting decrease. These changes are likely be precursory phenomena disastrous earthquake.
Remarkable numbers of microbial cells have been observed in global shallow to deep subseafloor sediments. Accumulating evidence indicates that and ancient sediments harbor living life, where the flux nutrients energy are extremely low. However, their physiology requirements remain largely unknown. We used stable isotope tracer incubation nanometer-scale secondary ion MS investigate dynamics carbon nitrogen assimilation activities individual from 219-m-deep lower Pleistocene (460,000 y old)...
We have prepared an artificial mixture of 3He and 4He to be used as internal standard for precise 3He/4He measurements terrestrial mantle-derived samples. The is named HESJ (He Standard Japan). ratio was determined by obtaining the weighted average repeated analyses from five machines in four laboratories Japan. recommended value relative air (R/Ra) 20.63 ± 0.10. available all researchers.
Geochemical characteristics of hydrothermal fluids in the Iheya North field, mid-Okinawa Trough, was investigated. Twelve-years observation reveals temporal variation vent fluid chemistry potentially controlled by temporally varying pattern phase-separation and -segregation, while constant Element/Cl ratios among periods chimneys indicate stable chemical composition source prior to undergoing phase-separation. The high K contents estimated are typical arc-backarc systems due reaction with...
Initial subduction-related boninitic magmatism occurred between 48 and 44 Ma in the Izu–Bonin–Mariana (IBM) arc. High-Mg adakites low-Ca boninites have been dredged from Bonin Ridge fore-arc seamount. Whole-rock 40Ar/ 39Ar ages suggest that boninite (44·0 ± 1·4 Ma) adakite (43·1 1·0 40·8 0·8 overlapped, or slightly later than magmatism. The are high-Mg andesites exhibit U-shaped rare earth element (REE) patterns with an elevated average Mg# of 0·78 [Mg# = Mg/(Mg + Fe) molar ratio] Ni content...
The Mg/Ca ratio within foraminiferal calcareous tests (shells) is widely used to reconstruct past seawater temperature. However, recent studies reported that the organic components a test affect distribution. In this study, we have measured Mg/Ca, Sr/Ca, and Ba/Ca ratios planktonic foraminifera Pulleniatina obliquiloculata by using NanoSIMS (secondary ion mass spectrometer (SIMS)), which has excellent spatial resolution (∼1 μ m) allows us compare distribution of chemical compositions with...
Abstract Evaluation of volcanic and hydrothermal fluxes to the surface environments is important elucidate geochemical cycle sulphur evolution ocean chemistry. This paper presents S/ 3 He ratios vesicles in mid-ocean ridge (MOR) basalt glass together with high-temperature fluids calculate flux 100 Gmol/y at MOR. The gases show 720 arc volcanoes (ARC) a contribution from mantle 2.9%, which calculated as 21 Gmol/y. C/S ratio 12 MOR ARC comparable inventory, suggests that these elements...
Mt Ontake in central Japan suddenly erupted on 27(th) September 2014, killing 57 people with 6 still missing. It was a hydro-volcanic eruption and new magmatic material not detected. There were no precursor signals such as seismicity edifice inflation. is difficult to predict eruptions because they are local phenomena that only affect limited area surrounding the explosive vent. Here we report long-term helium anomaly measured hot springs close cone. Helium-3 most sensitive tracer of...
Abstract Geochemical monitoring of groundwater and soil gas emission pointed out precursor and/or coseismic anomalies noble gases associated with earthquakes, but there was lack plausible physico-chemical basis. A laboratory experiment rock fracturing conducted, is no quantitative connection between the results observation in field. We report here deep helium related to 2016 Kumamoto earthquake, which an inland crustal earthquake a strike-slip fault shallow hypocenter (10 km depth) close...
Some benthic foraminiferal species are reportedly capable of nitrate storage and denitrification, however, little is known about incorporation subsequent utilization within their cell. In this study, we investigated where how much 15N or 34S were assimilated into cells possible endobionts after incubation with isotopically labeled sulfate in dysoxic anoxic conditions. After two weeks incubation, specimens fixed prepared for Transmission Electron Microscopy (TEM) correlative nanometer-scale...
The isotopic composition of nitrogen bears important information concerning the fate this volatile in mantle‐crust‐atmosphere system. Based on compositions mid‐ocean ridge basalts and pristine diamonds, a δ 15 N value about ‐ 5±2‰ (where = [( N/ 14 ) sample / ( N) air − 1] × 1000) is assigned to upper mantle. In contrast, origin has not been well documented subduction zones. We report here values, 2 36 Ar, 40 Ar/ Ar ratios comprehensive suite samples from along convergent plate boundaries...
Understanding the origin and evolution of near-Earth asteroids (NEAs) is an issue scientific interest practical importance because NEAs are potentially hazardous to Earth. However, when how formed their evolutionary history remain enigmas. Here, we report U-Pb systematics Itokawa particles for first time. Ion microprobe analyses seven phosphate grains from a single particle provide isochron age 4.64 ± 0.18 billion years (1σ). This ancient thought represent thermal metamorphism Itokawa's...