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Umeda, Koji; Asamori, Koichi; Kobori, Kazuo; Hama, Yuki
no journal, ,
Earthquake swarms, often interpreted to result from fluids invading the brittle seismogenic zone, have seismicity patterns that are significantly different from an aftershock sequence. Following the Mw 9.0 Tohoku-Oki earthquake, an unusual, shallow normal-faulting swarm sequence occurred near the Pacific coast in the southeastern Tohoku district. An integrated approach combining geophysical and geochemical methods was utilized to establish the presence of aqueous fluids around the seismic source region and their derivation.
Sasao, Eiji; Ishibashi, Masayuki; Yuguchi, Takashi
no journal, ,
Fractures in the crystalline rock (i.e. granite) can act as groundwater pathways. Thus, understanding of the fracture characteristics is an important subject for the disposal of high-level nuclear waste. Geological setting and formation process of the granite influence the fracture characteristics. Thus, this study discuss the relation between "formation of fracture and infilling mineral" and geological history from emplacement to present in the Toki granite, central Japan. The Toki granite cooled rapidly during 20 m.y. after the emplacement to about 250
C, and then the granite underwent exhumation with slowly cooling during 50-30 m.y. until the subaerial exposure. Brittle fracture occurred below about 300-400C in a cooling granite, and the fracture fillings also occurred below such temperature. The fracture fillings show hydrothermal chlorite and calcite and meteoric water-derived calcite. Chloritization temperature (200-300C) is an indicator of formation temperature of the hydrothermal infillings. The meteoric water-derived calcite occurred in a period between the sedimentation of the Mizunami Group (20 Ma) and present.
Sueoka, Shigeru; Shimada, Koji; Ishimaru, Tsuneari; Niwa, Masakazu; Yasue, Kenichi; Umeda, Koji; Danhara, Toru*; Iwano, Hideki*
no journal, ,
no abstracts in English
Sueoka, Shigeru; Tagami, Takahiro*
no journal, ,
no abstracts in English
Watanabe, Tsuyoshi; Okuyama, Satoshi; Asamori, Koichi
no journal, ,
no abstracts in English
Munemoto, Takashi; Omori, Kazuaki; Iwatsuki, Teruki
no journal, ,
no abstracts in English
Ikeda, Hisashi*; Shibata, Kenji; Murakami, Takuma; Kokubu, Yoko; Katsuta, Nagayoshi*
no journal, ,
no abstracts in English
Hatano, Nozomi*; Yoshida, Koki*; Sasao, Eiji; Yasue, Kenichi; Adachi, Yoshiko*; Iwano, Hideki*; Danhara, Toru*
no journal, ,
The Miocene Tokiguchi Porcelain Clay Formation consists mainly of muddy sediments, which were deposited in the tectonical-controlled small inland basin in the southern part of the Gifu Prefecture, central Japan. This research focuses the U-Pb radiometric ages of detrital zircon grains in the sandy sediments in this formation in order to clarify the provenance variations by radio metric ages. Additionally bulk rock assemblage of the hinterland was estimated by the REE chemical composition of the muddy sediments. The age of detrital zircon grains were concentrated at the 12-15 and 70-80Ma. Some grains showed 200, 1700, 1800, 1900 and 2900 Ma. REE composition of the muddy sediments indicates various source rocks in the hinterland including basic, intermediate and felsic rocks. The wide range of age assemblage of detrital zircons shows significant difference, implying provenance variation. Also REE geochemistry is indicative of various source rock assemblage in the hinterland.
Otani, Tomoyuki*; Yokoi, Kosuke*; Okazaki, Kazunari*; Nishimura, Yuki*; Kojima, Satoru*; Kuboshima, Koji*; Sasao, Eiji
no journal, ,
The orientation of microcracks was measured using the MIU-3 core penetrating the Tsukiyoshi fault to clarify the relation of the microcrack distribution near the fault. Attitude of microcracks in quartz grains in granite are measured under the optical microscope with the universal stage using three perpendicular thin sections. The healed microcracks was probably formed prior to the sealed microcracks. Both healed and sealed microcracks with moderate dip appears near the fault. The distribution of microcracks with moderate dip shows that the preferred orientation of microcracks near the fault is different from that far from the fault. The distribution of the sealed microcracks with moderate dip is narrower than that of the healed microcracks. This shows that the healed microcracks with moderate dip was developed in the intact granite at the earlier stage of the faulting history, and the sealed microcracks was in the weak fault zone which has repeated rupturing and healing at the later.
Katori, Takuma*; Kobayashi, Kenta*; Yasue, Kenichi; Niwa, Masakazu; Komatsu, Tetsuya; Hosoya, Takashi*; Sasao, Eiji
no journal, ,
Understanding fault zone evolution is important for constructing the topographical and geological model for a time scale more than one million year. We analyzed fault rocks of the Byobuyama fault in Tono area by several methods including structural analysis in the field and using optical microscope, determination of mineral composition based on X-ray diffraction analysis, and chemical composition analysis using an X-ray fluorescence instrument. Based on these analyses, studied fault rocks could record several stages of fault activity under different depths and stress regimes.
Shimada, Koji
no journal, ,
In this preliminary study, more objective discrimination between orientations of small crush zones was carried out by means of directional statistics. Fitted number of mixture components of von Mises distribution is eight. A probability distribution function curve of eight components mixture shows two peaks. Crush zones principally depict dextral sense of shear along the system beta, and sinistral one along the system alpha-3. Plastically deformed biotite grains are observed in both crush zones. Deformation temperature of them seems to be higher. Statistically comparable development, nearly orthorhombic symmetry, and cross cutting relationship between the two systems suggest the development of crush zones in conjugate manner. This movement picture is inconsistent with continuing E-W shortening during late Quaternary. These lines of evidence suggest that crush zones observed at the site of Monju are old geologic structure.
Martin, A. J.*; Asamori, Koichi; Ishimaru, Tsuneari; Umeda, Koji
no journal, ,
Assessing the stability of the geological environment including the spatio-temporal distribution of active faulting is of particular concern in the context of site selection of a radioactive waste repository. In order to assess the spatio-temporal distribution of active faults, one typically starts by looking at mapped active faults to estimate spatial frequencies and orientations. However, active faults listed in current databases do not represent a complete picture of active faulting, as not all active faults have a surface reputure, and their existence might be unknown. In this case, additional datasets are needed that may imply the existance of active faulting. The Bayesian approach can be used to construct probablistic models from mulitple datasets in order to assess the likelihood of given natural phenomena occuring over defined time periods. We have been developing such a Bayesian model for new active fault segment formation in the Western Tottori district as a case study.
Shimizu, Mayuko; Tanikawa, Wataru*; Hamada, Yohei*; Kameda, Jun*; Yamaguchi, Asuka*; Kimura, Gaku*
no journal, ,
no abstracts in English
Katata, Genki; Grote, R.*; Zeeman, M. J.*; Mauder, M.*; Ota, Masakazu; Lu, H.*; Kiese, R.*
no journal, ,
We coupled a multi-layer atmosphere-SOiL-VEGetation model (SOLVEG) with a detail snow scheme and grass growth scheme to investigate snow-free grassland dynamics. We applied the modified SOLVEG to pre-alpine grassland sites in Germany for a year with an exceptional small amount of snowfall. The modified model reproduced temporal changes in observations of surface energy and CO
fluxes, soil temperature and moisture, and aboveground biomass. Our simulations and measurements demonstrate that grasses at lower elevation are not dormant and continuously assimilate atmospheric CO even in the middle of winter season. On the other hand, dead leaf biomass increases due to frosts over cold snow-free days. As a result, snow-free wintertime carbon uptake almost balanced with wintertime soil respiration. However, under temperature rise conditions, grass ecosystems act as a strong sink of CO from winter to early spring due to a decrease of frost damages of foliage.
Nishizawa, Yukiyasu; Yoshida, Mami; Sanada, Yukihisa; Torii, Tatsuo
no journal, ,
Many radioactive substances were released by the Fukushima Daiichi Nuclear Power Plant accident occurred on March 11, 2011 in the atmosphere. A lot of short half-life nuclides which are 
I, 
Te, etc., in addition to longer half- lived nuclides such as 
Cs and 
Cs. The estimated release amount of these nuclides from the reactor 1st to 3rd unit is reported, but it's found to be quite different in the short half-lived nuclides by the reactor units. Because the radioactivity ratio of Cs and Cs was slight different between the reactor units, it can be considered that the valuable source is obtained by the measurement of Cs/Cs ratio in the environment around the Fukushima Daiichi Nuclear Power Station at the present stage when the nuclides with short half-lives had already decayed. We have measured high-resolution 
-ray spectrum using an unmanned helicopter equipped with LaBr
(Ce) detector in a 3-km range from the power station which was near to the release source of the radioactive cesium. Because the LaBr(Ce) detector has high resolution of rays, the discrimination of many nuclides is possible. In addition, there is extremely much number of the data provided by the distribution measurement with the unmanned helicopter. Because a new map was illustrated by the analysis of the Cs/Cs ratio, we report the outline.
Torii, Tatsuo; Sanada, Yukihisa; Yamada, Tsutomu; Orita, Tadashi; Muraoka, Koji*; Sato, Masayuki*; Watanabe, Akira*; Kume, Kyo*; Hasegawa, Takashi*; Sugita, Takeshi*
no journal, ,
Energetic radiation caused by thunderstorm activity is observed at various places, such as the ground, high mountain areas, and artificial satellites. In order to investigate the radiation source and its energy distribution, we measured energetic radiation by a sounding balloon, an airplane, and the ground observation. On the measurement inside the thundercloud, we conducted a sounding observation using a radiosonde mounted two GM tubes (for -rays, and for 
/-rays), in addition to meteorological instruments. The balloon passed through a region of strong echoes in a thundercloud shown by radar image, at which time an increase in counting rate of the GM tube about 2 orders of magnitude occurred at the altitude from 5 km to 7.5 km. Furthermore, the counting rate of 2 GM tubes indicated the tendency different depending on movement of a balloon. This result suggests that the ratio for the -rays (energetic photons) of the beta-rays (energetic electrons) varies according to the place in the thundercloud. Then, we measured the variation of the energetic radiation from the top of the thundercloud using an airplane. At this time, we used two NaI detectors different in the size. We performed the radiation measurement by flying around the thunderclouds at 12 - 14 km in height by the observation in the summer. Moreover, in the winter season, we flew 5 - 6 km in height and measured the radiation around the thunderclouds. Furthermore, we carried out a ground observation of the energetic rays during winter thunderstorm at a coastal area facing the Sea of Japan. Two types of the energetic radiation have been observed at this time. We report the outline of these measurements and analysis in the session of the JpGU meeting.
Watanabe, Takayoshi; Oyama, Takuya; Ishii, Yasuo; Niizato, Tadafumi; Abe, Hironobu; Mitachi, Katsuaki; Sasaki, Yoshito; Kitamura, Akihiro
no journal, ,
For an estimate of movement from forest to living spheres, it is important to understand value of movement of soil and radioactive Cs from forest. We measured volumes of deposit with 3D laser scanner in an erosion control dam in Namie town, Fukushima prefecture on August 29, 2013 and December 3, 2014. As a result of measurement, an amount of increase of sediment for 15 months is 0.5 m
. A denudation rate is 0.02 mm/year. This value is on the same level with denudation rates in meadows and forest, 10
10
mm/year (Fujiwara et al, 1999). And it is estimated that a variation of radioactive Cs is Cs-137: 200 MBq, Cs-134: 80 MBq.
Fujihara, Satoru*; Kirita, Fumio; Kawaji, Kaoru*; Yamazaki, Toshihiko; Uryu, Mitsuru; Yasuda, Masahiro
no journal, ,
no abstracts in English
Kametaka, Masao*; Sakai, Toru*; Inada, Noriyuki*; Tanaka, Yumiko*; Okazaki, Kazuhiko*; Suzuki, Yuji*; Aoki, Kazuhiro; Tanaka, Yoshihiro; Seshimo, Kazuyoshi; Nakayama, Kazuhiko
no journal, ,
no abstracts in English
Aoki, Kazuhiro; Seshimo, Kazuyoshi; Tanaka, Yoshihiro; Kametaka, Masao*; Sakai, Toru*; Okazaki, Kazuhiko*; Shimamoto, Toshihiko*
no journal, ,
no abstracts in English