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Journal Articles

Seismic subsidence near the source region of the 1662 Kanbun Hyuganada Sea earthquake; Geochemical, stratigraphical, chronological, and paleontological evidences in Miyazaki Plain, southwest Japan

Niwa, Masakazu; Kamataki, Takanobu*; Kurosawa, Hideki*; Kokubu, Yoko; Ikuta, Masafumi*

Island Arc, 29(1), p.e12341_1 - e12341_26, 2020/01

 Times Cited Count:4 Percentile:33.2(Geosciences, Multidisciplinary)

Based on detailed geochemical and paleontological analyses for lowland sediments in the Miyazaki Plain, southwest Japan, we clearly identified environmental change from the lower terrestrial sediments to the upper shallow marine sediments. Radiocarbon ages and tephra data suggest that the environmental change is attributed to local subsidence due to the 1662 Kanbun Hyuganada Sea Earthquake shown in historical records. This findings are important for historical earthquake studies because the study area is a part of the expected focal region of megathrust earthquakes along the Nankai Trough.

JAEA Reports

Geological and topographical data concerning normal faults (Kawaminami Fault) in the northern Miyazaki Plain, Southern Kyushu, Japan

Niwa, Masakazu; Kurosawa, Hideki*; Kosaka, Hideki*; Ikuta, Masafumi*; Takatori, Ryoichi*

JAEA-Data/Code 2017-009, 71 Pages, 2017/06

JAEA-Data-Code-2017-009.pdf:13.8MB
JAEA-Data-Code-2017-009-appendix(CD-ROM).zip:50.09MB

Changes of stress state due to the 2011 off the Pacific Coast of Tohoku Earthquake triggered normal displacements of faults that have not been regarded as active faults. In this study, geological survey for normal faults in coastal region was conducted in order to understand the mechanism of reactivation of inactive faults triggered by megathrust earthquakes. This report includes topographical and geological data obtained by field works in and around the Kawaminami Fault in northern margin of the Miyazaki Plain, with results of microscopic examination, analyses of X-ray diffraction and particle size distribution for clayey samples, analyses of tephra and plant opal, and radiocarbon dating.

Journal Articles

Identification of pumice derived from historic eruption in the same volcano; Case study for the Sakurajima-Bunmei tephra in the Miyazaki Plain

Ikuta, Masafumi*; Niwa, Masakazu; Danhara, Toru*; Yamashita, Toru*; Maruyama, Seiji*; Kamataki, Takanobu*; Kobayashi, Tetsuo*; Kurosawa, Hideki*; Kokubu, Yoko; Hirata, Takafumi*

Chishitsugaku Zasshi, 122(3), p.89 - 107, 2016/03

We carried out mineral composition analysis, morphological classification of volcanic glass shards and refractive index measurements of the glass shards and orthopyroxene from the eruption products from Sakurajima volcano. In this study, refractive indexes of hydrated and non-hydrated parts within each individual glass shard were measured separately. This measurements in consideration of hydration in glass shards made possible distinct discrimination of the pumice samples from the three eruption events of Bunmei, An-ei, and Taisho. Pumice layers in the core samples obtained from the southern part of the Miyazaki Plain were also identified as the Sakurajima-Bunmei tephra by the above mentioned analyses, and also by the data of radiocarbon dating for coaly materials included in the pumice layers. Occurrences of the pumice layers suggest that the Sakurajima-Bunmei tephra could have reached the southern part of Miyazaki Plain as pumice falls.

JAEA Reports

Analytical data of Holocene sediments in the Miyazaki Plain, Southern Kyushu, Japan

Ikuta, Masafumi; Niwa, Masakazu; Takatori, Ryoichi*; Kamataki, Takanobu*; Kurosawa, Hideki*

JAEA-Data/Code 2014-002, 246 Pages, 2014/06

JAEA-Data-Code-2014-002-01.pdf:17.7MB
JAEA-Data-Code-2014-002-02.pdf:49.07MB
JAEA-Data-Code-2014-002-03.pdf:39.02MB
JAEA-Data-Code-2014-002-04.pdf:36.25MB
JAEA-Data-Code-2014-002-05.pdf:22.17MB
JAEA-Data-Code-2014-002-appendix(DVD).zip:1642.4MB

The Miyazaki Plain, facing the Hyuga-nada, had been attacked repeatedly by historical tsunami events induced by the giant earthquakes centered in the Hyuga-nada or Nankai Trough. However, scientific studies concerning the tsunami events are still poor in this area. Disappearance of subsurface sediments due to fast uplift rates in the Miyazaki Plain is considered to make difficult to proceed such studies. This database shows the result of the study for Holocene sediments in the Miyazaki Plain in 2012, including chemical composition analysis of absorbed water, microfossil identification, description of tephra deposits and radiocarbon dating, as well as geological description of drilled cores. It is closely related to the study for the reactivation of coastal geological faults caused by the giant subduction zone earthquakes.

JAEA Reports

Annual report for research on geosphere stability for long-term isolation of radioactive waste in fiscal years 2012

Yasue, Kenichi; Asamori, Koichi; Niwa, Masakazu; Hanamuro, Takahiro; Kokubu, Yoko; Sueoka, Shigeru; Makuuchi, Ayumu; Ikuta, Masafumi; Matsubara, Akihiro; Tamura, Hajimu; et al.

JAEA-Research 2013-047, 109 Pages, 2014/03

JAEA-Research-2013-047.pdf:6.81MB

This annual report documents the progress of R&D in the 3rd fiscal year during the JAEA 2nd Midterm Plan (FY 2010 - 2014) to provide the scientific base for assessing geosphere stability for long-term isolation of the high-level radioactive waste. The planned framework is structured into the following categories: (1) development and systematization of investigation techniques for selecting suitable sites in geosphere stability, (2) development, application and verification of prediction models for evaluating the changes of geological environment in thermal, hydraulic, mechanical and geochemical conditions for a long period of time, and (3) development of new dating techniques for providing information about geologic history and the timing of geologic events. In this paper, the current status of R&D activities with previous scientific and technological progress is summarized.

JAEA Reports

Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific programme for fiscal year 2013)

Yasue, Kenichi; Asamori, Koichi; Niwa, Masakazu; Hanamuro, Takahiro; Kokubu, Yoko; Makuuchi, Ayumu; Ikuta, Masafumi; Matsubara, Akihiro; Ishimaru, Tsuneari; Umeda, Koji

JAEA-Review 2013-023, 42 Pages, 2013/10

JAEA-Review-2013-023.pdf:2.82MB

The concept of geological disposal of HLW in Japan is based on a multi-barrier system which combines a stable geological environment with a robust barrier system. Potential geological host formations and their surroundings are chosen, in particular, for their long-term stability, taking into account the fact that Japan is located in a tectonically active zone. This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of HLW in JAEA, in fiscal year 2013. The objectives and contents in fiscal year 2013 are described in detail based on the outline of 5 years plan (fiscal years 2010-2014). In addition, the planned framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques.

Oral presentation

Approach for understanding the Holocene upheaval and subsidence in the Miyazaki Plain

Niwa, Masakazu; Ikuta, Masafumi; Takatori, Ryoichi; Kamataki, Takanobu*; Kurosawa, Hideki*

no journal, , 

Holocene uplift rate of the Miyazaki Plain was estimated based on the elevations and depositional ages of four terrace surface (Shimotajima I to IV surfaces; Nagaoka et al., 1991). However, age data are still poor except for the Shimotajima I surface. We report new data of detailed description of abandoned lagoon sediments of the Shimotajima II to IV surfaces.

Oral presentation

Characteristics of normal faults in coastal area; Case study in the Kawaminami Fault, southern Kyusyu

Ikuta, Masafumi; Niwa, Masakazu; Takatori, Ryoichi; Kurosawa, Hideki*; Kosaka, Hideki*

no journal, , 

Although there are several normal faults in coastal area on the Pacific side, normal faulting triggered by a large earthquake in plate convergence has never been reported until the earthquake in Fukushima, April 11, 2011. Therefore more case studies focused on normal faults are needed to assess the risk of fault activity in coastal areas. As such case study, we are doing geological and topographical surveys in the Kawaminami Fault, lying along the northern margin of the Miyazaki Plain.

Oral presentation

Depositional paleoenvironment and a historical earthquake in the Miyazaki plain, south Kyushu, Japan

Ikuta, Masafumi; Niwa, Masakazu; Takatori, Ryoichi*; Kamataki, Takanobu*; Tanabe, Hiroaki; Kurosawa, Hideki*

no journal, , 

After the 2011 Tohoku Earthquake, probability and scale of giant earthquakes in the sea off Japan have been re-examined. The Central Disaster Management Council of Japan proposed a source model of hypothetical Nankai trough giant earthquake including the Hyuganada region. Historical data show that the 1662 Hyuganada Earthquake caused tsunami inundating the offshore part of the Miyazaki City and subsidence of about 1m. Here we began first geological survey to examine the geological evidence showing such giant earthquake in the Miyazaki City. In this study, we identified the changes of the depositional environment indicating the regional subsidence due to the 1662 historical earthquake.

Oral presentation

Research on geosphere stability for long-term isolation of radioactive waste; Development of models for long-term estimation and effective assessment

Ikuta, Masafumi; Niwa, Masakazu; Kamataki, Takanobu*; Takatori, Ryoichi*

no journal, , 

no abstracts in English

Oral presentation

Subsidence and a change of depositional environment by the 1662 Hyuganada earthquake in southern Miyazaki Plain

Ikuta, Masafumi; Sato, Yoshiki; Niwa, Masakazu; Kamataki, Takanobu*; Kurosawa, Hideki*; Takatori, Ryoichi*

no journal, , 

A lot of great earthquakes have caused in the Hyuganada and the Nankai trough. According to historical records of documents, the 1662 Kanbun Hyuganada earthquake, had caused serious damage and natural calamity. Around the estuary of the Kaeda-gawa River, the tsunami had reached to about 4 to 5meter height, and ground subsided about 1meter.Shimayama region which is located in the estuary of the Kaeda-gawa River, was formed an intrusive arm of the sea occurred by this subside event. Some historical records of documents and landscape pictures show that the 1662 Kanbun Hyuganada earthquake changed topography and depositional environment in this area extremely. However, there is no case study of this evidence. So, we did multiple borings in the abandoned lagoon sediments and tried to restore depositional environment around the subsided area by some analysis methods such as microfossils and chemistry to use boring cores. These results will be presented in this session.

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