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Yamada, Kunimi; Hanamuro, Takahiro; Tagami, Takahiro*; Yamada, Ryuji*; Umeda, Koji
no journal, ,
no abstracts in English
Sawada, Atsushi; Sato, Hisashi; Tetsu, Keiichi*; Sakamoto, Kazuhiko*
no journal, ,
no abstracts in English
Illman, W. A.*; Liu, X.*; Yeh, J.*; Ando, Kenichi*; Takeuchi, Shinji; Saegusa, Hiromitsu
no journal, ,
Two cross-hole tests were conducted at separate locations in deep boreholes at the MIU construction site in central Japan. We analyze the two cross-hole hydraulic tests using the Transient Hydraulic Tomography (THT) code of Zhu and Yeh [2005] to compute the hydraulic conductivity (K) and specific storage (Ss) distributions as well as their uncertainties in three-dimensions. The equivalent K and Ss were obtained using the asymptotic analysis served as the initial parameter estimates for the 3D stochastic inverse modeling effort. Results show 2 distinct high K and low Ss zones that are continuous over distances ranging from 550 - 1,200 m, which delineate 2 separate fault zones. The fault zones that are imaged through THT correlate well with available geological data and drawdown records. The analysis of the tests with the THT code also identified a low K zone which corresponds with a known fault zone trending NNW and has been found to compartmentalize groundwater flow at the site.
Umeda, Koji
no journal, ,
A wide-band magnetotelluric survey was carried out with a 50 km long MT profile running across the Omine Mountains in order to image the deep crustal structure of the Kumano Acidic Rocks and the Omine Granitic Rocks. A body with high resistivity (more than 1000 
) is clearly visible in the subsurface shallower than 20 km, which corresponds to the distribution of the Omine Granitic Rocks and the western part of the Kumano Acidic Rocks. The resistive body extends to about 20 km depth and widens with increasing depth. The model suggests that these two igneous complexes are connected in the subsurface rather than discrete resistive body corresponds to either igneous complex. Radiometric ages, geochemical compositions and other geological data also support that the resistive body represents the fossil of large silicic magma system in relation to the Kumano-Omine volcano-plutonic complex.
Kawamura, Makoto; Umeda, Koji; Oi, Takao; Ishimaru, Tsuneari; Niizato, Tadafumi; Yasue, Kenichi; Makino, Hitoshi
no journal, ,
Torii, Tatsuo; Sugita, Takeshi*; Muraki, Yasushi*
no journal, ,
The dose rate of the 
-rays increases in association with the activities of the thunderstorm. To investigate the time profile of the radiations during the winter thunderstorms, four sets of the radiation detectors were prepared which consist of the long proportional counters. These detectors have different characteristics of the response for the energy of the incident particles by mounting different thick shielding covers. Electric field was also measured by using a field mill. As a result, the following two types of the radiation enhancements have been found during the winter thunderstorm activities; the gradual variation of photon intensity with energy of a few MeV, and the burst type of the radiation that is attributed to the injection of high energy photons with the energy over 10 MeV.
Maekawa, Keisuke; Karasaki, Kenji*; Takasu, Tamio*
no journal, ,
It is important for safety assessment of high-level radioactive waste geologic disposal to understand groundwater flow in deep underground accurately. In order to understand the behavior of seawater intrusion into freshwater in deep underground, we constructed a laboratory equipment, "Mini-MACRO" (MAss transport Characterization in host ROck). We created several cases of experimental conditions to observe the seawater intrusion behavior into two-layered stratum against various hydraulic gradients and densities of saltwater. We confirmed that the results using this equipment match numerical results under simple heterogeneous condition.
Karasaki, Kenji*; Maekawa, Keisuke
no journal, ,
We have modeled laboratory experiments of saltwater intrusion, similar to the so-called Henry Problem, using TOUGH2/EOS7. In general, the simulation showed good agreement to the experiment including the transient advancement and the final profile of the saltwater wedge that showed little dispersion in a homogeneous case. In a two-layer heterogeneous case, however, the simulation could not reproduce the experiment in one aspect. In the experiment, the fast-moving colored saltwater traveling in the higher permeability layer was observed encroaching into the lower permeability layer below. However, at this writing, we have not been able to reproduce this phenomenon, which could be caused by some instability or heterogeneity within the layers.
Torii, Tatsuo
no journal, ,
In order to investigate the generation of energetic photons which originate in thunderstorm electric fields, we have calculated the behavior of electrons and photons in electric fields with Monte Carlo method. In case of the calculation for the energetic electrons emitted in the atmosphere, the electron and photon fluxes have increased greatly in the region with high electric field. Then, we have carried out the Monte Carlo transport calculations of the 
and rays emitted by radon progeny products, as a source of energetic electrons, in thundercloud electric fields. From the calculated results, these products can serve as the source of a considerable amount of energetic electrons, because the radon progeny products form a large part of the energetic electrons in the atmosphere.