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Yamada, Kunimi; Kogiso, Tetsu*; Uesugi, Kentaro*; Hirata, Takafumi*
no journal, ,
no abstracts in English
Niwa, Masakazu; Takeuchi, Ryuji; Onoe, Hironori; Asamori, Koichi; Umeda, Koji; Sugihara, Kozo
no journal, ,
Groundwater level changes associated with the 2011 off the Pacific coast of Tohoku Earthquake are observed in the almost boreholes in and around the MIU site. All boreholes arranged away from the MIU showed drawdown ranging from 1 to 5 m. It is consistent with the volumetric strain changes calculated from the fault models associated with the Tohoku earthquake. In contrast, groundwater levels were elevated up to 15 m in the boreholes localized in the vicinity of the MIU. Dilatation caused by an earthquake is possible to induce crack opening and subsequent permeability increase. This mechanism could cause the anomalous elevation of groundwater level within the MIU site, as a temporal recovery of continuously artificial drawdowned groundwater level.
Yasue, Kenichi; Doke, Ryosuke; Niwa, Masakazu; Tanikawa, Shinichi; Nakayasu, Akio; Niizato, Tadafumi; Asamori, Koichi; Ishimaru, Tsuneari; Umeda, Koji
no journal, ,
A started age of present faulting pattern is meaningful to suggest the beginning of neotectonic regime such as evolution stages of mountains. The onset times of faulting in the Japanese Islands are estimated using previous study data. We used a calculation method which is the total displacement subdivided by the slip rate. We also used information of the strata indicating the appearance of the faulting. The main results are shown as follows : (1) In northeast Japan, reverse faulting in the N-S direction started since about 3 million years ago. (2) In southwest Japan, the onset times of faulting are estimated in the Kinki district and the northern part of the Izu peninsula, which are younger than those in other regions. (3) There appear to be many active faults in the Niigata-Kobe Tectonic Zone which started since about 1 million years ago.
Mizuno, Takashi; Takeuchi, Ryuji; Tsuruta, Tadahiko; Matsuoka, Toshiyuki; Saegusa, Hiromitsu
no journal, ,
Moriya, Koichi; Koarashi, Jun; Atarashi-Andoh, Mariko; Moriizumi, Jun*; Yamazawa, Hiromi*; Ishizuka, Shigehiro*
no journal, ,
no abstracts in English