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.

Reliable measurement method to reveal a peculiar dielectric dispersion in wet rocks by means of ACROSS

Matsumoto, Hiroshi*; Shigeta, Naotaka; Kumazawa, Mineo; Nakajima, Takahiro

Handbook of Geophysical Exploration; Seismic Exploration, Vol.40, p.121 - 133, 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.

Frequency comb spectroscopy for reliable evaluation of vibration characteristics of nuclear facilities by means of ACROSS, 1; Basic line of approach for system identification and health 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

Reliable and strict evaluation is demanded to guarantee the safety of nuclear facilities against earthquake vibrations, in particular. Usually the necessary data have been acquired by determining the natural frequency and attenuation characteristics by utilizing microseisms as an excitation agent of the vibration. The presence of measurement errors and estimation bias has been inherent and problematic in this approach. Here we try to make a break through by introducing ACROSS technology, which have been providing very accurate and reliable data on subsurface, i.e., geologic targets. In this paper, we report the relevant strategy, general concept of this approach. The technical subjects on measurement system and also a potential method of analyzing data are reported in the subsequent two papers.

Development of ACROSS (Accurately Controlled, Routinely Operated, Signal System) to realize constant monitoring the invisible Earth's interiors by means of stationary coherent elastic and electromagnetic waves

Kumazawa, Mineo; Kunitomo, Takahiro; Nakajima, Takahiro; Tsuruga, Kayoko*; Hasada, Yoko*; Nagao, Hiromichi*; Matsumoto, Hiroshi*; Kasahara, Junzo*; Fujii, Naoyuki; Shigeta, Naotaka

JAEA-Research 2007-033, 155 Pages, 2007/03

JAEA-Research-2007-033.pdf:11.04MB

The developmental study made at Tono Geoscience Center under the Earthquake Frontier Research Project since 1996 is reported for a brand new technology system called ACROSS (Accurately Controlled, Routinely Operated, Signal System). Several examples of the field application are demonstrated by the test experiments at Tono Mine site. After the developmental works of 10 years, the ACROSS is brought to be a practical method applied to the remote monitoring of temporal variation of underground states at the Horonobe Underground Research Laboratory and also it is being applied to the expected focal region of the coming Tokai earthquake near Hamaoka in Shizuoka prefecture. Whereas ACROSS technology is not mature enough yet, it is shown to be a potential and versatile methodology applied even for the health monitoring of the construction such as building strongly coupled with the ground in addition to the underground study.

An Examination of detection possibilities of the EM signals transmitted from the submarine cable to monitor the conductivity in the crust

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

Conductivity Anomaly Kenkyukai 2006-Nen Rombunshu, p.119 - 120, 2006/03

We examined the possibility for the application of the submarine cables off the coast of Toyohashi as a transmitting source of EM-ACROSS. We estimated the ACROSS signals reflected from the high conductivity layer 9 km below the seabed. The numerical calculations of the layered medium indicates that the signal from the layer could emerge with a few days observation of the electric field. The observable frequency range estimated by the assumed conductivity model is between 0.01 and 1 Hz.

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 Dense seismic array for acquisition of high quality in the ACROSS observation

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

IWAM04, 116 Pages, 2004/08

We are developing an active seismic monitoring methodology on the seismic ACROSS to detect any subtle change of geophysical properties in the Earth's crust. To demonstrate the availability of the seismic ACROSS, which uses coherent seismic waves actively, it may be the best to use several dense arrays routinely. In this study, we briefly review our seismic array observation system by the seismic ACROSS and their specifications, and report the latest results of array observation.

Development of EM-ACROSS and observed transfer function using this system

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

2004 Fall Meeting Program and Abstract, S33B-1096, 0 Pages, 2004/00

We have developed and tested a new electromagnetic sounding method, which is called EM-ACROSS (ElectroMagnetic - Accurately Controlled Routinely Operated Signal System). We carried out a field test using this system at Tono area, and acquired very accurate transfer function between the source and receiver. The estimated value of the ground conductivity is consistent with the previously reported values. From the phase of the transfer function for a month, we can see the correlation with the rainfall.

Overview of EM-ACROSS

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

Gekkan Chikyu Gogai, (47), 174 Pages, 2004/00

We introduce a new electromagnetic sounding method called EM-ACROSS (ElectroMagnetic - Accurately Controlled Routinely Operated Signal System). The feature of the propagation of the elecromagnetic waves is defferent from that of elastic waves. We introduce the present state of the development of a system at Tono Geoscience Center. We estimate the posivility of the exploration of deep Earth's crust.