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Journal Articles

Manifestations of upwelling mantle flow on the Earth's surface

Asamori, Koichi; Umeda, Koji; Ninomiya, Atsushi*; Negi, Tateyuki

The Earth's Core; Structure, Properties and Dynamics, p.79 - 94, 2011/07

Remarkable uplift of 1400 m during the Quaternary has been recognized in the Mesozoic crystalline mountains (Asahi Mountains) located on the back-arc side of the Northeast Japan Arc. Crustal and mantle structures beneath the mountains were imaged as a 2D resistivity model, using magnetotelluric survey. The resulting resistivity structure clearly indicates that an anomalous conductive body is present in the central part of the mountains. The conductor extends from the middle crust to the upper mantle. Also, helium isotope ratios were determined from free gas and groundwater samples collected in and around the mountains. The highest value is similar to those of MORB-type helium derived from mantle volatiles. These results provide strong evidence for the presence of a latent magma reservoir and related high-temperature aqueous fluids beneath the Asahi Mountains. The presence of a latent magma reservoir could lead to thinning of the brittle upper crust and the aqueous fluids could weaken the crustal rocks. Thus, contractive deformation could arise locally above the reservoir under compressive stress field. Although the uplift is considered to be controlled by active reverse faults on the west side of the mountains, the highest peak of the mountains is not located near the active faults, but rather is above the prominent conductive zone. It is concluded that the notable uplift of the mountains can mainly be attributed to locally anelastic deformation of the entire crust.

Journal Articles

An Efficient and effective stacking method for MT spectrum data; A Validation study using survey data

Negi, Tateyuki; Umeda, Koji; Matsuo, Koichi*; Asamori, Koichi; Yokoi, Koichi*; Ohara, Hidefumi*

Butsuri Tansa, 64(2), p.153 - 165, 2011/04

The wide band MT method is recognized as an effective method for identifying deep resistivity structures in the crust. In the method, natural variations in the electric and magnetic fields of the earth are acquired over a wide range of frequencies. World wide, thunderstorm activity produces magnetic fields at frequencies above 1Hz. These natural phenomena create strong MT source signals over the entire frequency spectrum. However, magnetic fields at frequencies below 1Hz activate intermittently, because they are caused by the interaction between solar wind and the magnetosphere and therefore, long recording times are required to obtain usable readings. In noisy regions, the signals may be contaminated by DC train signals and other coherent noise, such as occur in western Japan. When magnetic field data are contaminated by such noise, it is difficult to remove or segregate the contaminated data from the usable data. In the paper, we showed the validity of the new weighted stacking method using survey data contaminated by coherent noise.

JAEA Reports

Research on geosphere stability for long-term isolation of radioactive waste (Progress report for fiscal years 2005 - 2009: H22 report)

Kusano, Tomohiro; Asamori, Koichi; Kurosawa, Hideki; Kokubu, Yoko; Tanikawa, Shinichi; Negi, Tateyuki; Hanamuro, Takahiro; Yasue, Kenichi; Yamasaki, Seiko; Yamada, Kunimi; et al.

JAEA-Research 2010-044, 153 Pages, 2011/01

JAEA-Research-2010-044.pdf:12.53MB

This progress report (H22 report) documents progress made during JAEA 1st Midterm Plan (FY 2005 - 2009) to provide the scientific base for assessing geosphere stability for long-term isolation of the high-level radioactive waste. For the current 5-year R&D programme, three major goals have been defined as follows: (1) development and synthesis of investigation techniques for selecting suitable sites in geosphere stability, (2) development, application, and evaluation 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.

Journal Articles

A Large intraplate earthquake triggered by latent magmatism

Umeda, Koji; Asamori, Koichi; Negi, Tateyuki; Kusano, Tomohiro

Journal of Geophysical Research, 116(B1), p.B01207_1 - B01207_12, 2011/01

 Times Cited Count:15 Percentile:44.95(Geochemistry & Geophysics)

A magnitude ($$M$$$$_{j}$$) 7.3 intraplate earthquake occurred in the western Tottori area, southwest Japan, on 6 October 2000, where there was no apparent prefaulting subsurface indication of the source fault of the 2000 earthquake. Magnetotelluric soundings were taken in and around the aftershocks occurred in order to image 3D electrical resistivity structure at depths of up to 40 km, which could indicate an anomalous conductor in the crust to the upper mantle on the southwest side of the source fault. Free gas and dissolved gases collected from groundwater wells around the seismic source region are characterized by $$^{3}$$He/$$^{4}$$He ratios several times higher than the atmospheric value. Although alkali basalts of early Pleistocene age are sparsely distributed in the western Tottori area, the observed $$^{3}$$He/$$^{4}$$He ratios are higher than the calculated $$^{3}$$He/$$^{4}$$He ratio derived from the ancient magmatism, considering post-extrusive radiogenic ingrowth of $$^{4}$$He by decay of U and Th included in the magma. Therefore, it is concluded that the geophysical anomaly imaged to the southwest of the source fault is attributed to latent magmatism in the present-day subduction system. Aqueous fluids separated from the cooling crustal magma could cause deep low-frequency earthquakes around the Moho discontinuity and migrate into the brittle upper crust. In addition, the presence of aqueous fluid is expected to weaken the crustal materials. Locally anelastic deformation, implying notable compressive deformation in the E-W direction, was observed in the region where aftershocks were distributed. Under overpressure conditions, the existing fault could serve as a pathway for aqueous fluids expelled from magma with high $$^{3}$$He/$$^{4}$$He ratios, so that the upwelling of overpressurized fluids toward the Earth's surface results in the emanation of groundwaters with high $$^{3}$$He/$$^{4}$$He ratios along the trace of the source fault segments.

Journal Articles

An Efficient and effective stacking method for MT spectrum data; Effectiveness against coherent noise

Negi, Tateyuki; Umeda, Koji; Matsuo, Koichi*; Asamori, Koichi; Yokoi, Koichi*; Ohara, Hidefumi

Butsuri Tansa, 63(5), p.395 - 408, 2010/10

In the MT-survey, it is important for the reliability evaluation of inversion result to evaluate acquired data quality. We suggested new reliability parameters, "Predict Phase Error (PPE)", "Acquired Curve Roughness (ACR)", "Error Bar Level (EBL)" to evaluate acquired data quality that was depend on the skill and experience of MT surveyor. We examined the relation between noise level and numerically expressed parameters. As a result, extremely high correlation coefficient was recognized between noise level and PPE. PPE was expected available parameter to evaluate the noise level of acquired MT data. We suggested combination of PPE, ACR, and EBL to keep the objectivity and stability for the reliability evaluation.

JAEA Reports

Research plan on geosphere stability for long-term isolation of radioactive waste; Scientific programme for fiscal years 2010

Yasue, Kenichi; Asamori, Koichi; Yamada, Kunimi; Kokubu, Yoko; Yamasaki, Seiko; Kurosawa, Hideki; Tanikawa, Shinichi; Negi, Tateyuki; Kusano, Tomohiro; Hanamuro, Takahiro; et al.

JAEA-Review 2010-034, 42 Pages, 2010/09

JAEA-Review-2010-034.pdf:1.15MB

The concept of geological disposal of HLW in Japan is based on a multibarrier system which combines a stable geological environment with an engineered 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) for geosphere stability for long-term isolation of HLW in JAEA, in fiscal year 2010. The objectives and contents in fiscal year 2010 are described in detail based on the outline of 5 years plan (fiscal years 2010-2014). In addition, the plan 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.

JAEA Reports

Annual report for research on long-term stability of geological environments in FY2008

Kusano, Tomohiro; Asamori, Koichi; Kurosawa, Hideki; Tanikawa, Shinichi; Ninomiya, Atsushi; Negi, Tateyuki; Hanamuro, Takahiro; Yasue, Kenichi; Yamada, Kunimi; Ishimaru, Tsuneari; et al.

JAEA-Research 2009-072, 72 Pages, 2010/03

JAEA-Research-2009-072.pdf:11.27MB

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 2008, we carried out the following researches. For studies on faulting and seismic activity, we developed investigation techniques for evolutional history and activity of fault, and carried out case studies for development of effective assessment model in the fault zones. For volcanological and geothermal studies, we provided an integrated approach for detecting crustal magma and/or geothermal fluid in deep underground using geophysical and geochemical data. For the general evaluation study on uplift/denudation and climatic/sea-level change, we arranged investigation techniques for reconstruction of paleo-topography and paleo-climate, and to establish a simulation model for landform development. For studies on the long-term stability of the geological environments, we developed simulation techniques for groundwater flow related by crustal movement.

JAEA Reports

Annual report for research on long-term stability of geological environments in FY2007

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.

Journal Articles

Heat source for an amagmatic hydrothermal system, Noto Peninsula, Central Japan

Umeda, Koji; Ninomiya, Atsushi; Negi, Tateyuki

Journal of Geophysical Research, 114(B1), p.B01202_1 - B01202_10, 2009/01

Although there is no geological evidence of volcanism during the Pliocene and Quaternary in the Noto Peninsula, Central Japan, the peninsula has long been known to be unusual and atypical of non-volcanic regions, as indicated by the presence of high-temperature hot springs and the high geothermal gradient values of more than 50 K/km. In this work, we present new helium isotope data from the Noto Peninsula and examine a possible source of excess heat in this non-volcanic region, including geophysical evidence such as seismic velocity, resistivity structures, and heat flow data.

JAEA Reports

Annual report for research on long-term stability of geological environment in FY2006

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.

Journal Articles

Consideration on the evaluation of uncertainly for the MT 2-D image

Negi, Tateyuki; Umeda, Koji; Asamori, Koichi

Shadan Hojin Butsuri Tansa Gakkai Dai-118-Kai ((Heisei-21-Nendo Shunki) Gakujutsu Koenkai Rombunshu, p.198 - 201, 2008/05

MT-survey is used to be applied to the investigation of the geothermal resource, mineral resource, and oil. In recent years MT-survey has also been recognized as an effective method for the investigation of deep geological environments. However, due to the nature of magnetotulluric source, it is difficult to maintain data quality at all time in extremely noisy environment. Furthermore, expansion of urban area will provide an opportunity to acquire MT data in such environment. Therefore, it is important to be able to evaluate the uncertainly of inversion result using poor quality data. We show the new method of the uncertainly assessment of MT inversion results.

Journal Articles

Development of a method for robust smoothing of MT data and application to robust stacking methos for EDI files

Negi, Tateyuki; Umeda, Koji; Matsuo, Koichi*; Asamori, Koichi

Shadan Hojin Butsuri Tansa Gakkai Dai-117-Kai (Heisei-19-Nendo Shuki) Gakujutsu Koenkai Koen Rombunshu, p.195 - 198, 2007/10

MT survey has been applied to various fields in recent years. It is recognized as effective method to know deep resistivity structure. However, it is difficult to acquire interpretable quality data in highly noisy environments, because natural electromagnetic fields are used in the MT survey. To apply MT survey in such environments, it is important to develop robust stacking method to improve the quality of MT spectrum data. In the last SEGJ conference held in Spring 2007, we have reported effective robust stacking method based on MT reliability index shown in Negi et al (2005). In the fall conference, we report the development of robust smoothing method of MT data to compile with the robust stacking method. As a result of application to poor quality data, it was improved to interpretable quality data in short time. Therefore, it is expected to be effective and practical stacking method for the poor quality data.

JAEA Reports

None

*; *; *; *; *; Negi, Tateyuki*

PNC TJ1380 97-001, 1338 Pages, 1997/03

PNC-TJ1380-97-001.pdf:48.73MB

None

JAEA Reports

None

Shimo, Michito*; Yamamoto, Hajime*; *; Negi, Tateyuki*; Doe, T.*

PNC TJ1205 96-003, 340 Pages, 1996/03

PNC-TJ1205-96-003.pdf:8.4MB

None

Oral presentation

Geophysical and geochemical constraints on the heat source beneath the Mesozoic crystalline Iide Mountains, Northeast Japan

Umeda, Koji; Asamori, Koichi; Ninomiya, Atsushi; Negi, Tateyuki

no journal, , 

no abstracts in English

Oral presentation

Cryptic magmatism indicated by resistivity structure beneath Asahi mountains, Northeast Japan; Implication to tectonics around the area

Ninomiya, Atsushi; Negi, Tateyuki; Umeda, Koji; Asamori, Koichi

no journal, , 

no abstracts in English

Oral presentation

Effective stacking method for MT spectrum data

Negi, Tateyuki; Umeda, Koji; Asamori, Koichi

no journal, , 

MT survey has been applied to various fields in recent years. It is recognized as effective method to know deep resistivity structure. However, it is difficult to acquire interpretable quality data in highly noisy environments, because natural electromagnetic fields are used in the MT survey. To apply MT survey in such environments, it is important to develop robust stacking method to improve the quality of MT spectrum data. We developed robust stacking method based on MT reliability index shown in Negi et al (2005). As a result of application to MT spectrum data contaminated by much noise, it was improved to interpretable quality data. Therefore, it is expected to be effective stacking method for the MT survey in highly noisy environments.

Oral presentation

Geoscientific research for long-term stability of the geological environment, Advanced technology for exploration of magma and hydrothermal fluid; Development of data processing technique for MT data

Negi, Tateyuki; Umeda, Koji

no journal, , 

MT survey has been applied to various fields in recent years. It is recognized as an effective method for identifying deep resistivity structures in the crust. However, it is difficult to acquire high quality data in highly noisy environments because natural electromagnetic fields are used in the MT survey. To apply MT survey in such environments, it is important to develop a robust stacking method to improve the quality of the MT spectrum data. At the last SEGJ conference held in Spring 2007, we have reported a new effective and robust stacking method based on MT reliability index (Negi et al., 2005). In this study, we report the development of the robust smoothing method for MT data to be with the robust stacking method for EDI files. Applied to poor quality data, it improved the data to interpretable data in a short time. Therefore, it is expected to be effective and practical method for improving poor quality data.

Oral presentation

Variations in the $$^{3}$$He/$$^{4}$$He ratios of hot springs on the Noto Peninsula, Central Japan

Umeda, Koji; Ninomiya, Atsushi; Negi, Tateyuki

no journal, , 

no abstracts in English

Oral presentation

MT survey for the deep resistivity structure, and the new method of the reliability assessment

Negi, Tateyuki; Umeda, Koji; Asamori, Koichi

no journal, , 

MT-survey is used to be applied to the investigation of the geothermal resource, mineral resource, and oil. In recent years MT-survey has also been recognized as an effective method for the investigation of deep geological environments. However, due to the nature of magnetotulluric source, it is difficult to maintain data quality at all time in extremely noisy environment. Furthermore, expansion of urban area will provide an opportunity to acquire MT data in such environment. Therefore, it is important to be able to evaluate the quality of acquired data numerically in order to evaluate the reliability of inversion result. We show the new method of the quality assessment of MT data, its effect to the inversion result, and the new method of the reliability assessment of MT inversion results.

32 (Records 1-20 displayed on this page)