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Kato, Nobuyoshi*; Tsusaka, Kimikazu; Nago, Makito*; Yamagami, Masahito*; Matsubara, Makoto*; Shigehiro, Michiko*; Aizawa, Takao*; Kamemura, Katsumi*
Chishitsu To Chosa, (139), p.17 - 22, 2014/04
no abstracts in English
Sugita, Yutaka; Sanada, Hiroyuki; Aizawa, Takao*; Ito, Shunichiro*
JAEA-Research 2011-043, 25 Pages, 2012/02
JAEA-Research-2011-043.pdf:3.18MBJP, 2010-116655 Patent publication (In Japanese)
A simplified seismic velocity survey system was developed for the repeat performance of surveys in conjunction with tunnel excavation, to monitor the various changes that occur in a rock mass around tunnels or galleries as they are excavated in the deep underground. The simplified seismic velocity survey system developed consists of a hammer to transfer seismic energy to the borehole wall and receivers installed and anchored in the borehole, and then backfilled. The hammer is operated with compressed air, necessitated by the potential presence of flammable gas such as methane. The system developed was used in the EDZ Experiment in a horizontal tunnel in the Horonobe URL. Changes in seismic velocity were monitored during and after excavation of the tunnel and the tomograms obtained are high quality. These results show that the system developed can provide the information needed to monitor the development and the variations in an EDZ.
Sugita, Yutaka; Nakamura, Takahiro; Sanada, Hiroyuki; Aizawa, Takao*; Ito, Shunichiro*
Materials Research Society Symposium Proceedings, Vol.1265, p.39 - 44, 2010/11
The creation of an excavation disturbed zone (EDZ) is expected around the gallery when the gallery is excavated in the underground to dispose the radioactive waste. In-situ EDZ experiment has been performed to determine the rock properties and width of the EDZ in 140m gallery at a depth of 140m below the surface at Horonobe URL. In the experiment, seismic tomography measurement was performed by using seismic source to observe width of the EDZ. Observation area is 3m square horizontal plane along the sidewall of the 140m gallery. During excavation of the 140m gallery, seismic tomography measurement was performed repeatedly with processing of excavation of the gallery, and the change of velocity distribution of the rock around the gallery was observed. Seismic tomography investigation caught the EDZ developed around the excavated gallery.
Niinuma, Iwao*; Aizawa, Takao*; Ito, Shunichiro*
JNC TJ7400 2005-042, 344 Pages, 2004/03
JNC-TJ7400-2005-042.PDF:50.98MB
A Vertical Seismic Profiling(VSP), Geophysical Logging and Borehole televiewer (BHTV) were performed in borehole 03RT-03. The objectives of this work are to obtain of the elastic wave response corresponding to fractures and fault zones in the granite, and to understand the application of VSP technique to survey continuity of fault zones or fractures in granite. The contents of this survey were presented in this report. In VSP survey, five shot points were set along the direction of borehole drilling. VSP processing and 3D imaging of seismic reflector were performed in order to obtain the continuity and directivity of fault zones or fractures. The events in seismic processing section, corresponding to fault zone or fractures in the granite, accepted by core information. The results of those processing were compared with the geological information acquired from the data of Geophysical logging and BHTV.
*; Aizawa, Takao*; *
JNC TJ7420 2000-006, 54 Pages, 2000/03
JNC-TJ7420-2000-006.pdf:16.6MB
no abstracts in English
Motoyama, Aoi*; Ogawa, Yasuo*; Uyeshima, Makoto*; Asamori, Koichi; Uchida, Toshihiro*; Hase, Hideaki*; Koyama, Takao*; Sakanaka, Shinya*; Yamaya, Yusuke*; Aizawa, Koki*; et al.
no journal, ,
no abstracts in English
Motoyama, Aoi*; Ichiki, Masahiro*; Ogawa, Yasuo*; Uyeshima, Makoto*; Asamori, Koichi; Uchida, Toshihiro*; Koyama, Takao*; Sakanaka, Shinya*; Hase, Hideaki*; Aizawa, Koki*; et al.
no journal, ,
We compiled the magnetotelluric (MT) and geomagnetic transfer function (GDS) data which were acquired by Uchida (2004), Umeda et al. (2008), Asamori et al. (2011), Uyeshima (private comm.) and Ogawa (private comm). The 118 observation sites locate in the study area. Both MT and GDS frequency response was used to model three-dimensional resistivity distribution of the southern Tohoku district, NE Japan. The resultant resistivity model reveals no conductor beneath the onshore forearc in Fukushima prefecture. The model rather shows resistor there with over several-thousand ohm-m, which corresponds to the Abukuma batholiths. Thus, our model indicates that the area only around Iwaki-city is peculiar forearc, where fluid migrates upward from deep crust.
Usui, Yoshiya*; Ueshima, Makoto*; Hase, Hideaki*; Ichihara, Hiroshi*; Aizawa, Koki*; Koyama, Takao*; Sakanaka, Shinya*; Ogawa, Tsutomu*; Yamaya, Yusuke*; Nishitani, Tadashi*; et al.
no journal, ,
In the back-arc area of the southern Tohoku region, there are several quaternary volcanos and active faults that have the potential to cause M7-class inland earthquakes. In the vicinity of some of the volcanoes, deep low-frequency earthquakes occur, implying the transfer of melt or aqueous fluid. So as to reveal the magma supply system around the area, it is important to reveal the distribution of the subsurface fluid. Also, understanding the fluid distribution helps elucidate the earthquake generation process. To delineate the subsurface electrical resistivity structure, the authors estimated the resistivity structure in the area by performing magnetotelluric surveys and generating the 3-D resistivity structure model with high resolution. In this study, the authors show the resultant electrical resistivity structure and discuss the subsurface fluid distribution as well as its relationship with the volcanic and seismic activities around the study area.
