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Hirouchi, Daisuke*; Yasue, Kenichi; Doke, Ryosuke*
Nihon Katsudanso Gakkai 2012-Nendo Shuki Gakujutsu Taikai Koen Yokoshu, p.52 - 53, 2012/11
no abstracts in English
Hirouchi, Daisuke*; Yasue, Kenichi; Uchida, Chikara*; Hiramatsu, Takahiro*; Taniguchi, Kaoru*; Sugito, Nobuhiko*; Kaneda, Heitaro*
Katsudanso Kenkyu, (27), p.201 - 209, 2007/06
The Yugamine fault, 10 km in length, is in the north-central part of the Atera fault zone. We studied Holocene activity of the Yugamine fault through a trenching survey. Some humic layers and fluvial gravels are exposed on the trench walls. The Yugamine fault has cut through these layers to form a linear depression on its NE side. From the structural evidence along the fault plane and angular unconformity, we recognize at least four faulting events in this trench.
Hirouchi, Daisuke*; Matsuta, Nobuhisa*; Ishiyama, Tatsuya*; Sugito, Nobuhiko*; Takeshita, Yoshihiro*; Mizutani, Kotaro*; Yasue, Kenichi*; Fujita, Natsuko; Sawa, Sho*; Doke, Ryosuke*; et al.
no journal, ,
no abstracts in English
Yasue, Kenichi; Hirouchi, Daisuke*; Kokubu, Yoko; Matsubara, Akihiro; Furusawa, Akira*
no journal, ,
This study proposes the exact identification method of faulting events. Radiocarbon ages of the black soil collected continuously from lower to upper part clarify the timing of faulting events. We sampled the black soil without space from the excavated trench wall of the active fault. The soil ages in footwall varied from 9,500 to 2,000 years ago with depth. The soil deposited at approximately a constant rate. However, there are partially the anomalous ages. The anomalies are probably caused by fault displacements, which means the collapse of hanging wall with old soil and the making of depression at the footwall side. The anomalous ages may suggest that faulting events took place in about 7,500, 6,000, 3,500, and 2,000 years ago. Our future research will be to apply this method to the soil of other active fault trench wall to clarify the timing of faulting events.
Wakasa, Sachi*; Ishiyama, Tatsuya*; Hirouchi, Daisuke*; Matsuta, Nobuhisa*; Fujita, Natsuko; Echigo, Tomoo*
no journal, ,
no abstracts in English
Mizutani, Kotaro*; Hirouchi, Daisuke*; Matsuta, Nobuhisa*; Ishiyama, Tatsuya*; Sugito, Nobuhiko*; Yasue, Kenichi*; Takeshita, Yoshihiro*; Fujita, Natsuko; Sawa, Sho*; Doke, Ryosuke*; et al.
no journal, ,
no abstracts in English
Hirouchi, Daisuke*; Matsuta, Nobuhisa*; Ishiyama, Tatsuya*; Yasue, Kenichi*; Sugito, Nobuhiko*; Takeshita, Yoshihiro*; Fujita, Natsuko; Sawa, Sho*; Mizutani, Kotaro*; Taniguchi, Kaoru*
no journal, ,
no abstracts in English
Yasue, Kenichi*; Harada, Shunsuke*; Kokubu, Yoko; Hirouchi, Daisuke*
no journal, ,
We present the results of a pit survey conducted in the middle part of the Atera fault zone and 
C dating of black soil. Samples were collected continuously from the black soil on both sides of the fault at intervals of approximately 5 cm in the depth direction. The dating sample was treated with hydrochloric acid and sodium hydroxide and separated into an alkali-soluble component (humic acid) and an insoluble component (humin). As a result of the dating, the age values generally become younger from the bottom to the surface. In detail, we can see parts where the age gradually become younger towards the surface, parts where the age are almost the same continuously, and parts where the age are reversed. The parts where the age gradually decreases toward the surface is considered to be a normal forest condition where black soil gradually forms over time. A succession of the same age values suggests the formation of a rapid deposition field. The age reversal suggests that older black soil was redeposited on top. These results indicate some event. For example, it is possible that old black soil was rapidly supplied from the upper layer after the fault displacement. We must carefully consider the type of event.
Yasue, Kenichi; Hirouchi, Daisuke*; Kokubu, Yoko; Matsubara, Akihiro; Furusawa, Akira*
no journal, ,
In order to clarify the stratigraphic correlation around the fault and the timing of faulting event, we carried out radiocarbon dating of the black soil sampled from the trench wall of the Atera Fault. The dating results show that the soil ages varies from 4,000 to 2,000 years with depth. Black soil was deposited at approximately constant rate each at both sides of the fault in 4,000-2,000 years ago. This indicates that the fault wasn't displaced during this period. In the upper part, there is no variation in ages of black soils with depth. This suggests that sedimentation rate was faster. One of the causes that the sedimentation rate around the fault suddenly changes is fault displacement. It is thought that the faulting was about 2,000 years ago. About this timing, it is necessary to consider in behavioral segments of Atera fault zone in detail.
Be dating of middle-late Pleistocene uplifted marine terraces in northern Pacific coast of Northeastern JapanWakasa, Sachi*; Ishiyama, Tatsuya*; Hirouchi, Daisuke*; Matsuta, Nobuhisa*; Fujita, Natsuko; Echigo, Tomoo*
no journal, ,
Surface exposure ages of marine and fluvial terraces based on in situ Be dating were determined to estimate formation ages and long-term rates of coastal uplift along the northern Pacific coast of Northeastern Japan. Surface exposure ages from Be concentrations in quartz calculated from the measured Be/
Be ratios commonly suggest slow in both sites, whereas steep dip domains on the marine terraces along the northern Sanriku coast may imply localized permanent strain accumulation.
Yasue, Kenichi; Hirouchi, Daisuke*; Matsubara, Akihiro; Kokubu, Yoko
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no abstracts in English
