The 16 September 2015 Chile Tsunami from the Post-Tsunami Survey and Numerical Modeling Perspectives     

Rafael Aránguiz  Gabriel González  Juan González  Patricio A. Catalán  Rodrigo Cienfuegos  Yuji Yagi  Ryo Okuwaki  Luisa Urra  Karla Contreras  Ian Del Rio  Camilo Rojas 《Pure and Applied Geophysics》2016,173(2):333-348

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Geographical distribution of helium isotope ratios in northeastern Japan   总被引：1，自引：0，他引：1  

Keika  Horiguchi  Sadato  Ueki  Yuji  Sano  Naoto  Takahata  Akira  Hasegawa  George  Igarashi 《Island Arc》2010,19(1):60-70

In order to study the precise geographical distribution of helium isotope ratios in northeastern Japan and compare it with geophysical data, we collected 43 gas and water samples from hot and mineral springs in the region where the ratio had never been reported, and measured the ³He/⁴He and ⁴He/²⁰Ne ratios of these samples. It was found that the ³He/⁴He ratios show clear contrasts between the forearc and the back-arc regions in the Tohoku district in northeastern Japan. In the forearc region, the ratios are smaller than 1 R_A (1 R_A = 1.4 × 10⁻⁶; R_A means the ³He/⁴He ratio of the atmosphere). On the other hand, those along the volcanic front and in the back-arc region are apparently higher. Moreover, we found a variation in the ³He/⁴He ratios along the volcanic front. In Miyagi Prefecture (38–39°N), the ratios range from 2 to 5 R_A. On the other hand, the ratios are less than 1 R_A in and around the southern border between Iwate and Akita Prefectures (39–39.5°N). Comparing the distribution of helium isotope ratios to results of recent geophysical studies, we found that the features in geographical distribution of helium isotope ratios are similar to those of seismic low-velocity zone distributions and high Qp⁻¹ distributions in the uppermost mantle. These observations strongly suggest that the helium isotope ratios reflect the distribution of melts in the uppermost mantle and are a useful tool for investigating the origin, behavior, and distribution of deep fluids and melts.  相似文献   

HFSE-rich picritic rocks from the Mino accretionary complex,southwestern Japan     

Yuji?Ichiyama  Akira?IshiwatariEmail author 《Contributions to Mineralogy and Petrology》2005,149(4):373-387

Sills, pillow lavas and hyaloclastites of the HFSE-rich picrite and related rocks (ankaramite and basanite) occur in the Middle Permian cherts in the Mino Jurassic accretionary complex, southwestern Japan. These rocks show systematic trace element patterns enriched in incompatible elements, which indicate that the associated ankaramite and basanite are formed by the crystal fractionation from the picrite. The presence of the hyaloclastite in the chert sequence covering a large tholeiitic greenstone body indicates that the picrite was produced in an intraoceanic setting in the Middle Permian time subsequent to the extrusion of the voluminous oceanic island tholeiite. The Mino picrites resemble the Siberian meimechite and Polynesian picrites in its HFSE-rich chemical composition. The HFSE enrichment in these picrites cannot be explained by low degree of partial melting of primitive peridotite mantle only, and needs a source material involving recycled oceanic crust (eclogite). The differences in MgO content and in TiO₂/Al₂O₃ and Zr/Y ratios among the HFSE-rich picrites indicate that the melting pressure increases from the Polynesian picrite through Mino picrite to Siberian picrite. This may reflect the increasing thickness of the overlying lithosphere at the time and place of magmatism. The HFSE-rich picrites may be a product of a superplume event. The presence of HFSE-rich picrite in Mino and Siberia indicate that the superplume activities occur in both continental and oceanic settings in the Permian time.  相似文献   

Diurnal variations in streamflow and water quality during the summer dry season     

Daiji Kobayashi  Yuji Kodama  Yoshiyuki Ishii  Yumiko Tanaka  Keisuke Suzuki 《水文研究》1995,9(7):833-841

In a headwater basin covered with boreal forest in northern Japan, the summer dry flow was monitored each summer from 1985 to 1993. Streamflow and specific electrical conductance fluctuated diurnally and these variations were attributed to daytime evapotranspiration. In 1989, the daytime reduction in streamflow and conductance were accompanied by a reduction in the HCO^?₃ concentration. The low flow hydrograph was separated into two components using HCO^?₃ and Cl^? concentrations in August 1989, assuming low flow to be a mixture of delayed subsurface flow and of quick shallow flow. The slight diurnal variation in the ratio of shallow flow to subsurface flow caused the diurnal variation in conductance by changing the HCO^?₃ concentration.  相似文献   

10th annual report on the international status of engineering geology—year 2004-2005; encompassing hydrogeology, environmental geology and the applied geosciences     

Allen W. Hatheway  Yuji Kanaori 《Engineering Geology》2005,81(2):99-130

The year was particularly eventful in terms of the recognition of improved technologies impinging on the duties of the Engineering Geologist. National economies were strained to the limit under the pressure of the new world terrorist attacks and burgeoning populations. much of which stemmed from escapes from oppressive national regimes to the free world. The impacts of terrorism range from increased danger and costs of field work, to special design considerations and postponed and delayed project work.On the positive side, continued progress has been made in the means of recognition and professional development of our practitioners and in the general call for their work. Competent engineering geologists are in consistent demand, but the working conditions are not improved. A general deterioration of university funding, aggravated by bureaucratic excesses among administrators, have tended to make life miserable for dedicated faculty and a general move is afoot to cut back on the number of funded geology departments in North America and Europe. This situation has also been worsened by the general withdrawal of the mineral industries and by retraction of the petroleum companies from all but their most favored campuses.  相似文献   

Ion microprobe U–Pb dating of zircon with a 15 micrometer spatial resolution using NanoSIMS     

Naoto Takahata  Yukiyasu Tsutsumi  Yuji Sano 《Gondwana Research》2008,14(4):587

We developed a ²³⁸U–²⁰⁶Pb and ²⁰⁷Pb–²⁰⁶Pb zircon dating method using a Cameca NanoSIMS NS50 ion microprobe. A 7-to 9-nA O⁻ primary beam was used to sputter a 15-μm crater, and secondary positive ions were extracted for mass analysis using the Mattauch–Herzog geometry. The multicollector system was modified to detect ⁹⁰Zr⁺, ²⁰⁴Pb⁺, ²⁰⁶Pb⁺, ²³⁸U¹⁶O⁺, and ²³⁸U¹⁶O₂⁺ ions simultaneously. A mass resolution of about 4000 at 10% peak height and with a flat peak top was attained, and the sensitivity of Pb was about 4 cps·nA^− 1·ppm^− 1. A multicrystal zircon standard (QGNG) from South Australia with a U–Pb age of 1842 Ma was used as a reference for Pb⁺/UO⁺–UO₂⁺/UO⁺ calibration, and on the basis of the positive correlation between these ratios, we determined the sample ²⁰⁶Pb/²³⁸U ratios. ²⁰⁷Pb/²⁰⁶Pb ratios were measured by magnetic scanning in single-collector mode. The standard zircons 91500, from Canada, and SL13, from Sri Lanka, were analyzed against QGNG. Observed ²³⁸U–²⁰⁶Pb and ²⁰⁷Pb–²⁰⁶Pb ages agreed well with published ages within experimental error. Then, 16 zircon grains in a metamorphic rock from Nagasaki, Japan, were analyzed. Observed ages were compatible with SHRIMP ages, suggesting that the NanoSIMS with a 15-μm probe diameter is suitable for ion microprobe U–Pb zircon dating.  相似文献   

Fracturing mode analysis and relative age dating of faults by surface textures of quartz grains from fault gouges   总被引：5，自引：0，他引：5  

Yuji Kanaori 《Engineering Geology》1983,19(4):261-281

Surface textures of quartz grains taken from about 250 samples of fault gouges in faults ranging in length from several metres to several tens of metres with the faults extending several tens to several hundreds of kilometres in length, are examined by means of the scanning electron microscope and are categorized into four groups from I to IV, based on the smoothness of the surface, degree of undulation and development of cavities, as mentioned in a previous paper. Based on surface features of quartz grains from faults the geological age of movement of which is known, the groups I to IV are tentatively related to the age of formation of quartz grains and the period of formation of surface textures. This correlation makes it clear that quartz-grain surface textures are an important clue to dating a relative age of faulting. River patterns, striations, granular fracture surfaces, and dimple-like textures are observed to appear on less corroded surfaces of quartz grains from fault gouges. Fractographic analysis of these surfaces of quartz grains should be a clue to revealing the mode of fracture of the fault movement which released the quartz grains into the fault gouge.  相似文献   

Noble gas elemental and isotopic abundances in deep-sea trenches in the western Pacific     

George Igarashi  Masako Kodera  Minoru Ozima  Yuji Sano  Hiroshi Wakita  Jacques Boulgue 《Earth and Planetary Science Letters》1987,86(1)

Noble gas elemental and isotopic abundances were measured in seven deep-sea water samples from five different sampling sites in the Nankai Trough, the Japan Trench and the Kuril Trench. The samples were obtained by the manned submersible “Nautile”. Most of the sampling sites are associated with clam colonies and/or fluid venting. Excesses both in³He/⁴He ratio and He concentration are observed in a seawater sample collected a few kilometers off the clam colonies which were found at a depth of 3830 m at the mouth of the Tenryu Canyon. Concentrations of noble gases (Ne, Ar, Kr and Xe) in this sample show progressive depletion from Ne to Xe relative to those in 1°C air-saturated seawater, which can be attributed to mixing of hot water ( 15°C) with cold ambient water ( 1°C). Isotopic compositions of Ne, Ar, Kr and Xe in this sample are atmospheric. These observations may reflect venting of hot pore water around the Tenryu Canyon. All the other samples show a significant excess in concentration of all noble gases relative to 1°C air-saturated seawater and the isotopic compositions are atmospheric. This excess of noble gas concentrations may appear to be air contamination in the samples. However, results of hydrocarbon analyses of the Kaiko samples imply that such large amount of air contamination is improbable. Decomposition of gas hydrate in deep-sea sediments is a more likely explanation for the observed excess of noble gas concentration.  相似文献   

Precise temperature measurement of groundwater for earthquake-prediction study   总被引：2，自引：0，他引：2  

Yuji Nakamura  Hiroshi Wakita 《Pure and Applied Geophysics》1984,122(2-4):164-174

Precise measurements of groundwater temperature, with a resolution of 0.0001°C, have been made for the purpose of earthquake prediction at four water wells in the Tokai district in Japan. The characteristics of temporal variations in groundwater temperature differ from well to well. From records of a well located in an area where use of groundwater is heavy, movement of groundwater was sensed by temperature variations. By contrast, water temperatures in a 500 m well far from cultural areas were extremely steady, with fluctuations of less than 0.0005°C. This well appears to be suitable for monitoring possible temperature changes related to the occurrence of an impending large earthquake.  相似文献   

基于SKS分裂研究长白山区上地幔各向异性特征     

宋雨佳  盘晓东  康建红 《地质论评》2024,70(S1):129-130

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