Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Yasue, Kenichi; Takatori, Ryoichi*; Tanikawa, Shinichi*; Ninomiya, Atsushi*; Tanase, Atsushi*; Furusawa, Akira*; Tajikara, Masayoshi*
Chishitsugaku Zasshi, 120(12), p.435 - 445, 2014/12
Estimating the rate of change in landforms and geological environments due to erosion is important when assessing the safety of the geological disposal of high-level radioactive waste in Japan. The aim of this study is to develop an index of erosion rates in inland mountains. We focused on circular abandoned channels, which are old river valleys around detached meander cores formed by the cut-off of incised meandering rivers. The channels can be useful for estimating incision rates because they occur at a range of elevations throughout the Japanese Islands. We undertook a case study to determine the incision rate using a circular abandoned channel in the middle reaches of the Kumanogawa River in the Kii Peninsula, where many circular abandoned channels have been identified. We obtained undisturbed core samples of old river channel deposits and angular gravel deposits that overlie the circular abandoned channel. The old river channel deposits have been emergent since at least MIS5, based on an analysis of the soil color in angular gravel deposits. The incision rate, as calculated from this age and the difference in elevation between the abandoned and present channels, is less than about 0.9 m/ky. This study shows that analyses of circular abandoned channels can yield estimates of incision rates and potentially also uplift rates. More accurate estimates of incision rates require further studies of the dating and evolution of sediments that overlie circular abandoned channels.
Yasue, Kenichi; Tajikara, Masayoshi*; Tanikawa, Shinichi; Sugai, Toshihiko; Yamada, Koji*; Umeda, Koji
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 18(2), p.51 - 62, 2011/12
We attempt to improve the reliability of the TT method, quantitative estimation of inland uplift rate based on the model in which river bed elevation is controlled by the climate change. In order to recognize fluvial terraces in the glacial epoch, it is important to note that flood deposit and phytolith as indicators of the determination of the emergence horizon and the estimate of the paleoclimate, respectively. The identification of thick sediments suggesting the decline of the tractive force in the glacial epoch are also useful for highly accurate comparison and chronology of the terrace. This paper shows that the synthetic examination based on many data obtained by these techniques enables a highly accurate comparison and chronology of the terrace to estimate uplift for the last 100,000 years with high reliability.
Tajikara, Masayoshi*; Yasue, Kenichi; Yanagida, Makoto*; Furusawa, Akira*; Tanaka, Norifumi*; Morita, Yoshimune*; Sugai, Toshihiko
Chirigaku Hyoron, 84(2), p.118 - 130, 2011/03
Many papers reported that Quaternary climate and sea-level fluctuations have controlled riverbed elevation in the river basins in the northeastern Japan. However, in the southwestern Japan, such climatic-controlled riverbed fluctuations have not been reported, except a few reports based on uncertain chronological data. In this research, we investigated fluvial terraces along the Tokigawa river that flows through the low relief mountainous areas, and examined whether riverbed fluctuations similar to these in rivers in the northeastern Japan occurred in the river basin. We mapped fluvial terraces based on air photo analysis, and inferred the age and climate at the time of formation of these terraces based on 
C dating, tephra analysis, and pollen analysis. Based on results of these analyses, we concluded that the fluvial terraces in the river basin have been formed in consequence of the riverbed fluctuation linked to the climate change.
Tajikara, Masayoshi; Takada, Keita*; Furusawa, Akira*; Sugai, Toshihiko
Dai Yonki Kenkyu, 50(1), p.21 - 34, 2011/02
Three major fluvial terraces are developed well along the Kabura-gawa river, tributary of the Tone-gawa river. We detected cryptotephras in overbank and aeolian deposits covering the middle terrace gravels, and examined petrologic character. We also investigated petrologic character of the Iizuna-Kamitaru tephra (In-Kt) and the Iizuna-Nishiyama (In-Ny) tephra extracted from the outcrops near the Iizuna volcano. Based on these data, we identified possibly In-Kt and In-Ny tephra at the bottom of overbank deposits on the middle terrace of the Kabura-gawa river. This indicates that the middle terrace was formed through aggradation at glacial age of marine oxygen isotope stage 6. The Kabura-gawa river basin is located out of the previously reported distribution area of In-Kt. This fact implies that In-Kt is distributed more widely in the northern Kanto and southern Tohoku regions, and that In-Kt is useful as marker tephra of the middle Pleistocene in these regions.
Kusano, Tomohiro; Nohara, Tsuyoshi; Umeda, Koji; Ishimaru, Tsuneari; Hanamuro, Takahiro; Saito, Tatsuo; Yasue, Kenichi; Niwa, Masakazu; Shimada, Koji; Yamada, Kunimi; et al.
JAEA-Research 2009-022, 47 Pages, 2009/09
JAEA-Research-2009-022.pdf:48.94MB
The Japanese islands are located in the tectonically active Circum-Pacific Mobile Belt. As a result, Japan has a high frequency of earthquakes and eruptions. Special consideration is given to the long-term stability of the geological environment, taking into account volcanism, faulting, uplift, denudation, climatic change and sea-level change in Japan. Development of research/prediction technologies for geotectonic events has been carried out to evaluate the long-term stability of the geological environment in Japan. In fiscal year 2007, we carried out the following researches, to confirm existence of the phenomena that have influences on geological disposal system (e.g., active faulting, volcanism), and to develop the investigation techniques to reconstruct the history of these phenomena. For studies of faulting and seismic activity, we developed the investigation techniques to research distribution of crush zone, process of faulting, activity, and so on. For volcanological and geothermal studies, we developed a technique for detecting crustal magma and/or geothermal fluid in deep underground. For studies of uplift/denudation and climatic/sea-level changes, we extracted investigation techniques for landform developments and uplift rate with river terraces.
Tajikara, Masayoshi; Ikeda, Yasutaka*; Nohara, Tsuyoshi
Jishin, 62(1), p.1 - 11, 2009/08
We estimated distribution of uplift rates during the last 150 kyrs around the focal region of the Iwate-Miyagi Nairiku Earthquake in 2008 (occurred at June 14, 2008; Mj 7.2, Mw 6.9), based on relative heights of fluvial/marine terraces. Active fault has not been mapped around this area, because clear fault scarp with large displacement does not exist. We showed that the uplift rates vary around the focal region and that the variation of uplift rates is related to the activities of the source fault of the Iwate-Miyagi Nairiku Earthquake in 2008. We estimated the vertical displacement rate of this fault as 0.4-0.5 mm/yr, based on difference of uplift rates on the both side of the source fault. We considered that the existence of (blind) active fault can be estimated even in the area with no clear fault scarp, by clarifying the distribution of uplift rates based on heights of fluvial/marine terraces.
Nohara, Tsuyoshi; Umeda, Koji; Sasao, Eiji; Hanamuro, Takahiro; Saito, Tatsuo; Yasue, Kenichi; Niwa, Masakazu; Mashima, Hidehisa*; Shimada, Koji; Yamada, Kunimi; et al.
JAEA-Research 2008-062, 61 Pages, 2008/07
JAEA-Research-2008-062.pdf:39.02MB
The Japanese islands are located in the tectonically active Circum-Pacific Mobile Belt. As a result, Japan has a high frequency of earthquakes and eruptions. Special consideration is given to the long-term stability of the geological environment in Japan. Development of research/prediction technologies for geotectonic events has been carried out to evaluate the long-term stability of the geological environment in Japan. During fiscal year 2006, we carried out the following researches, to confirm existence of the phenomena that have influences on geological disposal system, and to develop the research techniques to reconstruct the history of these phenomena. For studies of active faulting and seismic activity, we reviewed the existing techniques to research past activities and distribution of active faults (migration, extension, development process of a deformation zone). For volcanological and geothermal studies, we extracted a technique for detecting crustal magma and/or geothermal fluid in deep underground using geophysical and geochemical data, and models assessing the likelihood of future volcanism and its influence on geological environment. For studies of uplift/denudation and climatic/sea-level change, we constructed conceptual models such as landform development model.
Umeda, Koji; Oi, Takao; Osawa, Hideaki; Oyama, Takuya; Oda, Chie; Kamei, Gento; Kuji, Masayoshi*; Kurosawa, Hideki; Kobayashi, Yasushi; Sasaki, Yasuo; et al.
JAEA-Review 2007-050, 82 Pages, 2007/12
JAEA-Review-2007-050.pdf:28.56MB
This report shows the annual report which shows the summarized results and topic outline of each project on geological disposal technology in the fiscal year of 2006.
Tajikara, Masayoshi
no journal, ,
no abstracts in English
Tajikara, Masayoshi; Takada, Keita*; Nohara, Tsuyoshi
no journal, ,
no abstracts in English
Yasue, Kenichi; Sanga, Tomoji*; Nogami, Michio*; Tajikara, Masayoshi; Niizato, Tadafumi
no journal, ,
This paper presents the results of simulation of longitudinal river profile. Fast, we show that the longitudinal river profile is simulated in simplified model. Next, we simulated actual rivers by the same algorithm as the simplified model. This simulation shows that erosion rate and position of erosional front are different in each river. We think that Lithology influence the difference of erosional process in the river profile.
Tajikara, Masayoshi; Takada, Keita*; Furusawa, Akira*; Morita, Yoshimune*; Sugai, Toshihiko*
no journal, ,
We investigated fluvial terraces along the Kaburakawa River, in order to clarify the model of fluvial terrace development. Based on air photo analysis, fluvial terraces in the study area were classified into four categories (Q1-Q4). Existing papers reported that Q3 was formed in Marin Oxygen Isotope Stage (MIS) 2. In this study, we found a fragment of tree which is identified as 
or 
. This fact indicates that Q3 was formed in relatively cold age. Q2 is distributed at higher level than Q3. We found Iizuna-Kamitaru Tephra (Iz-Kt) at the lowermost part of aeolian deposits or uppermost part of overbank deposits in some outcrops of Q2 deposits. Since Iz-Kt is believed to fall at boundary of MIS 5 and 6, we concluded that Q2 deposits was accumulated in MIS 6 and that Q2 was incised in MIS 5.
Yasue, Kenichi; Tajikara, Masayoshi
no journal, ,
no abstracts in English
Niwa, Yuichi*; Tajikara, Masayoshi; Yasue, Kenichi; Ogami, Takashi*; Sugai, Toshihiko*
no journal, ,
no abstracts in English
Ogami, Takashi*; Tajikara, Masayoshi; Yasue, Kenichi; Niwa, Yuichi*; Sugai, Toshihiko*
no journal, ,
no abstracts in English
Tajikara, Masayoshi; Yasue, Kenichi; Yanagida, Makoto*; Sugai, Toshihiko; Morita, Yoshimune*; Furusawa, Akira*
no journal, ,
no abstracts in English
Yasue, Kenichi; Tajikara, Masayoshi; Saegusa, Hiromitsu; Niwa, Masakazu; Kurosawa, Hideki; Kusano, Tomohiro
no journal, ,
The stability of geological environments is influenced by natural events such as uplift, denudation, and climate variation. It is important for the geological disposal of nuclear wastes to assess the stability of geological environments. The purpose of this study is to establish the comprehensive techniques and method to evaluate the effects of topographic and climatic variations on groundwater flow condition. For this purpose, we developed the following techniques. (1) Research techniques for paleo-topography and paleo-climate (2) Modeling and simulation techniques for landform development (3) Simulation techniques of groundwater flow in consideration of the time-variation of geological environment. In this presentation, we introduce briefly the some of research results.
Niwa, Yuichi*; Sugai, Toshihiko; Ogami, Takashi*; Tajikara, Masayoshi; Yasue, Kenichi; Fujiwara, Osamu*
no journal, ,
no abstracts in English
Saito, Tatsuo; Nakatsuka, Noboru; Nohara, Tsuyoshi; Tajikara, Masayoshi; Yasue, Kenichi
no journal, ,
no abstracts in English
Saegusa, Hiromitsu; Yasue, Kenichi; Mizuno, Takashi; Takeuchi, Ryuji; Tajikara, Masayoshi; Kurosawa, Hideki
no journal, ,
no abstracts in English
