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Doke, Ryosuke; Tanikawa, Shinichi; Yasue, Kenichi; Nakayasu, Akio; Niizato, Tadafumi; Umeda, Koji; Tanaka, Takenobu*
Katsudanso Kenkyu, (37), p.1 - 15, 2012/09
Based on the collection and analysis of existing information, we clarified a spatial distribution of started age of present faulting pattern on active fault in Japanese Islands. The number of active faults which started its activities are gradually increased from about 3 Ma, dramatically increased after 1.5 Ma, and peaked at around 0.5 Ma. After 1.5 Ma, active faults which types of activity or trends are different from previously started active faults are developed. Therefore, there are plural types of active faults in the present tectonic field in Japan. After the peak around 0.5 Ma, newly developed active faults are decreased. It is possibly that newly developed active faults are undetectable; therefore, it is needed to develop new technics for detecting and assessing non-distinguishing active faults.
Doke, Ryosuke; Yasue, Kenichi; Nakayasu, Akio; Niizato, Tadafumi; Tanikawa, Shinichi; Tanaka, Takenobu*; Aoki, Michinori*; Sekiya, Ayako*
JAEA-Research 2011-031, 109 Pages, 2011/12
JAEA-Research-2011-031.pdf:7.23MB
In this study, existing information related to methods for the estimation of the beginning age of the faulting in the present faulting pattern on the active fault were collected and reviewed. A principle of method, noticing points and technical know-hows in the application of the methods, data uncertainty, and so on were extracted from the existing information. Based on these extracted information, task-flows indicating working process on the estimation of the beginning age for the faulting of the active fault were illustrated on each method. Additionally, the distribution map of the beginning age with accuracy of faulting in the present faulting pattern on the active fault was illustrated.
Nakayasu, Akio; Niizato, Tadafumi; Yasue, Kenichi; Doke, Ryosuke; Shigehiro, Michiko*; Tanaka, Takenobu*; Aoki, Michinori*; Sekiya, Ayako*
JAEA-Research 2010-056, 116 Pages, 2011/02
JAEA-Research-2010-056.pdf:28.28MB
The investigation methods for characterizing natural events and processes in a coastal field have been extracted on the basis of analysis of previous research. Collected information is classified into three groups according to characteristics of natural events/processes and investigation methods. First group is the methods for evaluation of uplift, subsidence and sedimentation rates. Second group is the methods for evaluation ob denudation rates. The third group is the methods for reconstruction of the climatic and sea-level changes. Based on an analysis of the above information, investigation method that can be applied to a coastal region was extracted. The methods and indices are as follows: (1) Uplift rate: the heights of marine terraces are the most important index in an upheaval region. (2) Subsidence and sedimentation rate: the depths of strata underlying an alluvial plain are main indices in a subsidence region. (3) Denudation rate: the features of marine terrace are main indices and the inspection of denudation processes by the use of a numerical simulation is necessary. (4) Climate change: lacustrine deposits are main object for investigation. (5) Sea-level change: reconstruction of relative sea-level change curve including uplift/subsidence factor and paleography based on acoustic exploration and the investigation of marine terraces.
Ishii, Eiichi; Yasue, Kenichi; Tanaka, Takenobu*; Tsukui, Rota; Matsuo, Koichi*; Sugiyama, Kazutoshi*; Matsuo, Shigeaki*
Chishitsugaku Zasshi, 112(5), p.301 - 314, 2006/05
Fault zones have significant influences on ground water flow. It is important to understand the characteristics of fault zones for hydrogeological modeling. We investigated the hydrogeological property and the geological structure of the fault in Neogene siliceous sedimentary rocks of northern Hokkaido, using geological mappings, reflection seismic surveys, and audio-frequency magneto telluric surveys. The result of description at a fault outcrop suggests that the Omagari Fault is a fault zone of about 120 m width that consists of mainly damage zone and that is a permeable structure without the strong anisotropy in permeability. In addition, the result of magneto telluric surveys shows high-resistivity zones having a flower structure, and one of the high-resistivity zones corresponds to the position of the Omagari fault inferred from the results of the reflection seismic surveys and of the borehole investigations. These high resistivity zones overlap with the low saline concentration zones, and the overlapping suggests the infiltration of the fresh water from the surface into the deeper part through the Omagari Fault as permeable structures. Based on these results and on study of the hydrogeological property, the geological structure, and petrological characteristics in and around the fault, it seems that the fault is a sinistral oblique-slip fault with eastside uplift sense that is formed after late Pliocene to early Pleistocene, but the possibility of the previous activity needs to research, and that the fault is over-stepping at the surface and is converging in deep underground like a flower structure shape.
Doke, Ryosuke; Yasue, Kenichi; Nakayasu, Akio; Niizato, Tadafumi; Tanaka, Takenobu*
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