The Outline of the research and development of EM-ACROSS in Tono area

Nakajima, Takahiro; Kunitomo, Takahiro; Kumazawa, Mineo*; Nagao, Hiromichi*

JAEA-Research 2010-014, 66 Pages, 2010/07

JAEA-Research-2010-014.pdf:3.11MB

ACROSS(Accurately Controlled Routinely Operated Signal System) has developed to acquire the detailed information on the tectonically active zone. The technology for example the transmission and receiving technique, the data analysis and the interpretation technique of the ACROSS signal is able to apply not only to seismology but also to other field. We considered the ACROSS technology may apply to the engineering technology of the Mizunami Underground Research Laboratory (MIU) project, for example monitoring of the change of the geological environment around shafts and also the strength of the shaft concrete itself. It is planned that the examination for three years will be made from fiscal year 2007, and the new observation site around the MIU was established, and the data acquisition and data analysis have been carried out. This report compiled technical matters among the results obtained in the research and the development of the EM-ACROSS.

EM-ACROSS system and corresponding tensor transfer functions in diffusion field region

Nakajima, Takahiro; Kunitomo, Takahiro; Nagao, Hiromichi*; Kumazawa, Mineo; Shigeta, Naotaka

Handbook of Geophysical Exploration; Seismic Exploration, Vol.40, p.177 - 191, 2010/03

We have developed a new electromagnetic controlled source method for the monitoring of the electrical state in the ground. This is called EM-ACROSS (Electro Magnetic - Accurately Controlled Routinely Operated Signal System). The basic idea of the EM-ACROSS system can be used at any frequency ranges. We developed one of a system using two pair of current dipoles at Tono area, and this is designed for the survey below 500 Hz, where the electromagnetic field behaves as diffusion field. We carried out a field test using this system, and acquired extremely accurate tensor transfer function from the source to the receiver, which the distance is about 950 m. From the phase of the transfer function for a month, we can see the correlation with the rainfall.

Automatic travel time determination from a frequency-domain transfer function; The Sompi event analysis

Hasada, Yoko*; Kumazawa, Mineo; Tsuruga, Kayoko*; Kunitomo, Takahiro; Kasahara, Junzo*

Handbook of Geophysical Exploration; Seismic Exploration, Vol.40, p.381 - 395, 2010/03

Frequency comb spectroscopy for reliable evaluation of vibration characteristics of nuclear facilities by means of ACROSS, 2; Accurate measurements and monitoring

Nishida, Akemi; Suzuki, Yoshio; Hayashi, Sachiko; Kunitomo, Takahiro*; Kumazawa, Mineo*; Hasada, Yoko*

Dai-58-Kai Riron Oyo Rikigaku Koenkai Koen Rombunshu (CD-ROM), 2 Pages, 2009/06

ACROSS (Accurately Controlled, Routinely Operated, Signal System) is such a precise metrology of frequency response characteristics that the accurately controlled sinusoidal waves (acoustic comb) is used as an input to the linear dynamic system, and induced vibration as an output is measured by the accelerometers synchronized accurately to input. This technology has been developed to be used on a routine basis for the subsurface structural analysis and state-monitoring of the geological targets. We discuss the theoretical background and the related subjects of applying this method to the artificial structures. Further we report the preliminary test experiments and results on the steel beam structure installed at TGC, JAEA.

Examination concerning application of ACROSS to engineering technology of the MIU project; Annual report, fiscal year 2007

Hasegawa, Ken; Kunitomo, Takahiro; Nakajima, Takahiro; Kumazawa, Mineo*; Kuroda, Hidetaka*; Iyatomi, Yosuke; Asai, Hideaki; Matsui, Hiroya

JAEA-Evaluation 2008-002, 60 Pages, 2009/03

JAEA-Evaluation-2008-002.pdf:4.92MB

We considered the ACROSS(Accurately Controlled Routinely Operated Signal System)technology may apply to the engineering technology of the MIU project, for example monitoring of the change of the geological environment around shafts and also the strength of the shaft concrete itself. It is planned that the examination for three years will be made from fiscal year 2007. The first year is expansion of the network of observation stations, the second year is data acquisition and last year is the analysis of data and evaluation of the ACROSS. In this report, we describe the results of fundamental studies of the ACROSS and the preparation of the ACROSS observation stations, performed in fiscal year 2007.

A Trial observation of the EM-ACROSS signal for the long-distance transmission

Nakajima, Takahiro; Nagao, Hiromichi*; Sayanagi, Keizo*; Noda, Yoichi*; Nagao, Toshiyasu*; Kumazawa, Mineo; Hasada, Yoko*

Tokai Daigaku Kaiyo Kenkyujo Kenkyu Hokoku, (28), p.21 - 28, 2007/03

http://www.iord.u-tokai.ac.jp/publication/kenpo/num_28/28_3nakajima.pdf

Observation test was successfully made on the faint EM-ACROSS signals transmitted through the Earth's crust over the distance of 30 km. We transmitted a set of three sine waves around 1Hz from the grounded wire source with the dipole moment 4A 150m. The signal level observed at the distance of 30 km was in the order of 0.01pT, which is 10 lower than the average level of environmental electromagnetic noise at the observation sites. The signal-to-noise ratio (S/N) of the observations becomes up to 5 by means of the optimized stacking of the raw observation data for the 40 days. signal-to-noise ratio (S/N) becomes larger. The result of this trial observation becomes a substantial experience for the monitoring of the area of earthquake generation or volcanoes in the future.

Automatic travel time determination for a transfer function measured by ACROSS using the Sompi event analysis

Hasada, Yoko; Kumazawa, Mineo; Tsuruga, Kayoko; Kunitomo, Takahiro; Kasahara, Junzo

Proceedings of 2nd International Workshop Active Geophysical Monitoring of the Earth Lithosphere (AMSEG 2005), p.35 - 37, 2005/09

The Sompi event analysis is a basic analysis method for ACROSS system, in which a set of time-localized events contained in the transfer function is extracted. Sompi is the Japanese word to mean existence or absence. We have established the fundamental algorithm and made revisions on the basis of Maximum Likelihood estimation (Hasada et al., 2004). To analyze numerous data acquired by continuous monitoring using ACROSS, automatic processing is necessary. We have attempted to improve the Sompi event analysis by using some additional techniques and examine the possibility of automatic travel time determination.

A Report of the 1st international workshop on 'Active Monitoring in the Solid Earth Geophysics'

Tsuruga, Kayoko; Ogawa, Katsuro*; Nagao, Hiromichi; Hasada, Yoko; Fujii, Naoyuki*; Kasahara, Junzo; Kumazawa, Mineo

Chigaku Zasshi, 114(4), p.659 - 664, 2005/04

https://doi.org/10.5026/jgeography.114.4_659

The 1st International Workshop on 'Active Monitoring in the Solid Earth Geophysics' was held in Mizunami city, Gifu, from June 30, 2004 to July 2. This paper discusses the significance of the active monitoring of the earth, and reports the summary of the workshop.

Evaluation of a dense seismic array for the acquisition of high quality data in the ACROSS observation

Tsuruga, Kayoko; Kunitomo, Takahiro; Hasada, Yoko; Kumazawa, Mineo; Shigeta, Naotaka; Kasahara, Junzo

2004 AGU Fall Meeting Program and Abstract, S31C-05, 0 Pages, 2004/00

We are developing an active monitoring methodology named ACROSS (Accurately Controlled Routinely Operated Signal System) to detect any subtle temporal change of physical properties in the Earth's interiors (Kumazawa et al., 2000). ACROSS is a comprehensive measurement system to determine continuously the transfer function of a linear system by means of the coherent signals. The combination of ACROSS transmission and array observation allow us to obtain the transfer function with high S/N (ratio of signal to noise) and S/B (ratio of signal to bias) in space and time. In this paper, we briefly review the specifications of our seismic array and report the latest results of the data analyses.

Travel time estimation from a transfer function in frequency domain: The revised Sompi event analysis

Hasada, Yoko; Kumazawa, Mineo; Tsuruga, Kayoko; Kunitomo, Takahiro

AGU 2004 Fall Meeting, 0 Pages, 2004/00

We have developed a method to extract "events" localized in time domain from a transfer function in frequency domain, which is a basic analysis method of ACROSS(Accurately Controlled Routinely Operated Signal System)and referred to as the Sompi event analysis. Though the validity of the Sompi event analysis is confirmed through various numerical tests especially for analysis of dispersive wave, there are some problems in practical application. Here we introduce a revised procedure by means of weighted least squares fitting, which is based on maximum likehood estimation.