K-Ar ages of an andesitic parallel dike swarm in the Takane area, Takayama City, Gifu Prefecture, Central Japan

Niwa, Masakazu; Ueki, Tadamasa*; Hoshi, Hiroyuki*; Sugisaki, Yuichi*; Yagi, Koshi*; Tozawa, Terumasa

Chishitsugaku Zasshi, 126(9), p.543 - 548, 2020/09

https://doi.org/10.5575/geosoc.2020.0021

A large number of paleomagnetic and chronological studies have contributed to the elucidation of the early Miocene clockwise rotation of Southwest Japan associated with the major opening of back-arc basins of the Japan Sea. Paleomagnetic data from an andesitic parallel dike swarm in the Takane area, Takayama City, Gifu Prefecture, Central Japan, were previously reported, showing the easterly deflection of the observed magnetization direction compared to an early Miocene expected paleomagnetic direction. This must represent the clockwise rotation during the opening of the Japan Sea, if the dike swarm was intruded before the opening event. Here, we report new K-Ar hornblende ages from an andesite dike of the dike swarm. These ages are statistically indistinguishable, indicating emplacement of the dike swarm before the clockwise rotation.

Tectonic tilting and coseismic subsidence along the Yoro fault system revealed from upper Holocene sequence in the Nobi plain, central Japan

Niwa, Yuichi*; Sugai, Toshihiko*; Yasue, Kenichi; Kokubu, Yoko

Chikei, 32(2), p.201 - 206, 2011/04

http://ci.nii.ac.jp/naid/110008671082

Analyses data of 24 shallow cores obtained from the Nobi plain, on the footwall side of the Yoro fault, suggest river channel change to west and temporal sea-level rise. The cores are represented by delta system and overlying fluvial system. Stacking patterns of the sedimentary units in the cross sections from the northern plain and C ages indicate the possibility that river channel change to the west has been occurred at ca. 2300 cal BP. High electrical conductivity, and brackish-marine diatom species identified in back swamp deposits in the cross section from the southern delta plain suggest temporal relative sea-level rise occurred at 1600 to 2700 cal BP. There is synchronism of the above-mentioned channel change and temporal sea-level rise events. Two possibility is considered as cause of these events; one is tectonic tilting and coseismic subsidence by the faulting at the Yoro fault, another is transgression at the Middle Ages.

Study on countermeasures for the elimination of re-criticality issue for the sodium cooled reactors; Results of the Studies in 2003

Kubo, Shigenobu; Tobita, Yoshiharu; Kawada, Kenichi; Onoda, Yuichi; Sato, Ikkenn; Kamiyama, Kenji; Ueda, Nobuyuki*; Fujita, Satoshi; Niwa, Hajime

JNC TN9400 2004-041, 135 Pages, 2004/07

JNC-TN9400-2004-041.pdf:17.3MB

This report shows the results of the study on countermeasures for the elimination of re-criticality issue for the sodium cooled reactors, which was conducted in 2003 as a part of the feasibility study phase II for the commercialization of fast reactors. A sort of analytical studies related to the in-vessel retention capability under the unprotected loss of flow condition was conducted for the large scale and medium scale sodium cooled reactors, aiming at establishing some promising concepts to resolve the re-criticality issue keeping consistency with the basic concept of the core and plant design. Major conclusions are as follows. ABLE concept, which is proposed as a measure to enhance the fuel discharge capability in the early transition phase, needs much time to initiate fuel discharge than wrapper tube failure. Therefore it is currently concluded that it is difficult to show clear perspective. A modified version of FAIDUS which has less drawbacks on the core and cycle performance and related R&Ds than original FAIDUS was proposed for further study. In-place retention and cooling in the core region is important from view point of reduction of R&D loads conceming post accident material relocation and cooling at the bottom of the reactor vessel. A possibility of which the in-vessel retention can be achieved by quantitatively clarifying the effect of the superior cooling potential of sodium was shown. Based on the currently available information related to FAIDUS and ABLE, possible candidates of experimental studies were shown. An initiating phase analysis for the metallic fuel core with 550C of core outlet temperature and 8 of sodium void worth resulted in mild consequence without prompt criticality. Although there is still large uncertainty in the early transition phase, it might be possible to avoid severe re-criticality. And it was shown that power excursion due to molten fuel sloshing might be milder than that of MOX fuel case.

The Progradation of the Holocene deltaic system along the Shonai River based on analysis of drilling cores and radiocarbon datings

Ogami, Takashi*; Tajikara, Masayoshi; Yasue, Kenichi; Niwa, Yuichi*; Sugai, Toshihiko*

no journal, , 

no abstracts in English

The Relationship between rapid relative sea-level rise recorded in the Holocene sequence in the Nobi Plain and coseismic subsidence

Niwa, Yuichi*; Sugai, Toshihiko; Ogami, Takashi*; Tajikara, Masayoshi; Yasue, Kenichi; Fujiwara, Osamu*

no journal, , 

no abstracts in English

Depositional environmental changes recorded in the Holocene sequence in the Nobi plain and their implication for the activity of the Yoro fault system, fringing the margine of the plain

Niwa, Yuichi*; Sugai, Toshihiko*; Ogami, Takashi*; Tajikara, Masayoshi*; Yasue, Kenichi; Fujiwara, Osamu*

no journal, , 

Analyses of drilling cores and C-14 ages from a lowland along the Yoro fault system fringing the Nobi plain suggest that five subsidence events occurred in the middle to late Holocene. The cores are represented by a prograding delta sequence that has formed on the footwall side of the Yoro fault system. Vertical changes of sedimentary facies, grain size distribution and Electronic Conductivity (EC) value of sediment samples suggest that temporal relative sea-level rise occurred. Trend of relative-sea level lowering during middle to late Holocene indicates that cause of these sea-level rise events can be coseismic subsidence.

Altitudinal distribution of the Last Interglacial Marine Formation in the central Kanto Plain, Japan

Miyamoto, Tatsuki*; Sugai, Toshihiko*; Komatsu, Tetsuya; Nakanishi, Toshimichi*; Niwa, Yuichi*; Hiura, Yuki

no journal, , 

no abstracts in English