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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.
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.
Nagao, Hiromichi*; Nakajima, Takahiro; Kumazawa, Mineo; Kunitomo, Takahiro
Handbook of Geophysical Exploration; Seismic Exploration, Vol.40, p.213 - 227, 2010/03
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.
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
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.
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.
Nagao, Hiromichi; Nakajima, Takahiro; Kunitomo, Takahiro; Kumazawa, Mineo; Nagao, Toshiyasu*; Sayanagi, Keizo*; Noda, Yoichi*; Harada, Makoto*
Proceedings of 2nd International Workshop Active Geophysical Monitoring of the Earth Lithosphere (AMSEG 2005), p.18 - 22, 2005/09
We have carried out an operation test of the EM-ACROSS at Tono, Japan. The EM-ACROSS signals were detected at a geomagnetic observatory 40km away from the transmitter located at Tono mine. The mean resistivity of the Toki granite formation is estimated to be 100 Ohm-m.
Tsuruga, Kayoko; Ogawa, Katsuro*; Nagao, Hiromichi; Hasada, Yoko; Fujii, Naoyuki*; Kasahara, Junzo; Kumazawa, Mineo
Chigaku Zasshi, 114(4), p.659 - 664, 2005/04
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.
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.
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.
Nakajima, Takahiro; Kunitomo, Takahiro; Nagao, Hiromichi; Kumazawa, Mineo; Shigeta, Naotaka
Gekkan Chikyu Gogai, (47), p.179 - 184, 2004/00
We have developed an electromagnetic sounding method, called EM-ACROSS (ElectroMagnetic - Accurately Controlled Routinely Operated Signal System), which can be used for the exploration of the frequency range below hundreds hertz. A trial observation has been done at Tono area for more than one year. We have obtained the accurate averaged transfer function, and also observed its temporal variation.
Nakajima, Takahiro; Kunitomo, Takahiro; Nagao, Hiromichi; Kumazawa, Mineo; Shigeta, Naotaka
International Workshop on Active Monitorig 2004, p.148 - 151, 2004/00
We have developed and tested a new electromagnetic sounding method, which is called EM-ACROSS (ElectroMagnetic - Accurately Controlled Routinely Operated Signal System). This system is designed for the survey below 500 Hz. We carried out a field test using this system at Tono area, and acquired very accurate transfer function between the source and receiver which the distance is about 700 m. From the phase of the transfer function for a month, we can see the correlation with the rainfall.
Nakajima, Takahiro; Kumazawa, Mineo; Shigeta, Naotaka; Kunitomo, Takahiro; Nagao, Hiromichi; Matsumoto, Hiroshi*
International Workshop on Active Monitoring 2004, p.100 - 103, 2004/00
We introduce a new observation system named EM-ACROSS (Electro-Magnetic Accurately Controlled Routinely Operated Signal System) for a monitoring the electrical state in the ground. Electromagnetic field has different feature from seismic wave, in a sense that electromagnetic field behaves not only as waves but also diffusion. We describe the overview of EM-ACROSS and the progress of its development at Tono Geoscience Center. We also note the possibility of the active monitoring of the crust using electromagnetic field.
Nakajima, Takahiro; Kunitomo, Takahiro; Nagao, Hiromichi; Kumazawa, Mineo
no journal, ,
We have developed and tested an electromagnetic sounding method, called EM-ACROSS (ElectroMagnetic - Accurately Controlled Rountinely Operated Signal System). We prepared two horizontal current dipole sources for two independent vector components of transmitting signal, in order to obtain the information on the anisotropy and lateral heterogeneity through the dependence of signal propagattion on azimuth and polarization. We report results of the observation and the analysis of the tensor transfer function obtained by the new observation system.
