Faculty Profiles - WATANABE Toshiki

Papers - WATANABE Toshiki

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Scattering analysis and estimation of structure heterogeneity in seismic exploration Invited

Vol. 29 ( 4 ) page： 227 - 231 2007

Continuous observation of seismic wave velocity and apparent velocity using a precise seismic array and ACROSS seismic source Reviewed

Saiga, A., Yamaoka, K., Kunitomo, T. and Watanabe, T.

Earth Planets and Space Vol. 58 ( 8 ) page： 993 - 1005 2006

Language：English Publishing type：Research paper (scientific journal)

We report the results of continuous monitoring.using a seismometer array.of the travel time of seismic waves generated by an ACROSS artificial seismic source. The seismometer array, which was deployed in a surface vault located 2.4 km from the source, recorded both direct P- and S-waves and refracted P- and Swaves that traveled along a velocity boundary between the granite basement and overlying sedimentary rocks. We analyzed temporal variation in differential travel time and apparent velocity for these phases for a period of 1 month and found significant temporal variation in the differential travel time. Most of the variation can be attributed to changes in environmental conditions, such as atmospheric temperature and rainfall. Variation is even observed in the seismogram that is located 50 m from the vibration source, although much smaller variation is observed in the vibration of the foundation to which the source is attached. The spectral study revealed that the effects of temperature and rainfall depend strongly on the frequency range used by ACROSS and that a large variation occurs in the 15- to 20-Hz range, especially between 17 and 20 Hz. The environmental effect on the temporal variation is comparable to the record of refracted S waves and that of a distance of 50 m, whereas a larger variation was observed in the direct S wave. This result shows that the signal is affected by the environmental change near the vibration source. The environmental effect can be drastically reduced when the signal from the 15- to 20-Hz range is eliminated in the analysis.

DOI： 10.1186/BF03352604

Seismic exploration at Fuji volcano with active sources : The outline of the experiment and the arrival time data Reviewed

Oikawa, J., Kagiyama, T., Tanaka, S., Miyamachi, H., Tsutsui, T., Ikeda, Y., Katayama, H., Matsuo, N., Oshima, H., Nishimura, Y., Yamamoto, K., Watanabe, T., Yamazaki, F., Watanabe, H., Fujii, T., Nakada, S., Takeo, M., Ohminato, T., Kaneko, T., Yoshimoto, M., Takeda, T., Koyama, E., Osada, N., Saka, M., Haneda, T., Hashimoto, S., Tsuji, H., Imoto, Y., Shimano, T., Furukawa, A., Sagiya, T., Fujii, I., Hayashi, Y., Miyajima, R., Yamada, M., Okuda, T., Itoh, T., Hashimoto, T., Maekawa, T., Suzuki, A., Itoh, T., Miura, Y., Ueki, S., Nishimura, T., Nita, K., Satoh, M., Simomura, Y., Nogami, K., Onizawa, S., Oyamada, H., Funasaki, J., Chikazawa, S., Fujiwara, K., Hamada, N., Aoki, G., Takagi, A., Yamamoto, T., Hayashi, Y., Kanao, M., Yamashita, M., Shimizu, H., Watanabe, A., Korenaga, M., Ohkura, T., Yoshikawa, S., Ikeda, S., Iguchi, M., Tameguri, T., Yakiwara, H., Hirano, S.

Bulletin of the Earthquake Research Institute Vol. 81 page： 71 - 94 2006

Continuous Active Seismic Observation using ACROSS Source and Seismometer Array Reviewed

Watanabe, T., Ikuta, R., Yamaoka, K., Soma, T. and Fujii, N.

Proceedings of the 8th SEGJ International Symposium -Imaging and interpretation- page： 369 - 372 2006

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

A team in Nagoya University has been extensively working on developing Accurately-Controlled Routinely-Operated Signal System (ACROSS) in order to monitor temporal variations in the subsurface properties. Continuous transmission of a controlled seismic signal from the seismic ACROSS source and the long-term observation of the waves propagating through the deeper crust and the plate boundary enable us to understand the time-variable phenomena such as slow-slip and deep tremor and to monitor the state of the plate boundary. We deployed a short-spam seismometer array in the "Aichi Prefectural Forest Park" in defunct Hourai Town (presently Shinshiro City) in eastern Aichi. The array, composed of 12 stations, is about 2 km wide in NS and 1 km wide in EW. The observation started from November, 2004 and terminated at the end of September, 2005. The seismic ACROSS source located at Toki has been operated to generate FM signal from 10 to 20 Hz in 50 seconds of period during the continous observation. After one or two weeks of data stacking, signals with a good S/N ratio were obtained using the surface seismometers, which is comparable to the data of the Hi-Net station deployed in a borehole. The transfer function clearly shows the P-wave, S-wave and their after-phases, having good correlation with the Hi-net data. A semblance analysis of array data shows the estimation of the azimuth and dip of the wave propagation and the apparent slowness. The waveform of after-phases, supposed to the reflected phase from the plate boundary, shows temporal changes during observation. Detailed analysis is underway, however, a possible explanation may be a correlation to the activity of deep low-frequency tremors in Tokai region.

DOI： 10.1190/segj082006-001.74

Time-lapse changes in tube and guided waves in cross-well Mallik experiment Reviewed

Bakulin, A., Korneev, V, Watanabe, T. and Ziatdinov, S.

Expanded Abstract of the 76th Annual Meeting, Society of Exploration Geophysicists page： 379 - 383 2006

南海トラフ沈みこみ帯の地殻比抵抗構造 Reviewed

木村俊則, 芦田讓, 後藤忠徳，笠谷貴史, 三ケ田均, 真田佳典, 渡辺俊樹, 山根一修

物理探査 Vol. 58 ( 3 ) page： 251 - 262 2005.8

Seismic Exploration by Using Active Sources at Kuchierabujima Volcano, Southwest Japan

Iguchi, M., Yamamoto, K., Hashimoto, T., Tsutsui, T., Tanaka, S., Onizawa, S., Aoki, Y., Watanabe, T., Ohkura, T., Shimizu, H., Yakiwara, H., Miyamachi, H., Hiramatsu, H., Tameguri, T., Takayama, T., Fukushima, M., Triastuty, H., Ishihara, K., Oshima, H., Suzuki, A., Maekawa, T., Kajii, T., Watanabe, Y., Ogiwara, Y., Nogami, K., Oikawa, M., Hirabayashi, J., Tsuji, H., Hiratao, Y., Okuda, T., Itoh, T., Yoshikawa, S., Inoue, H., Ikeda, S., Hori, M., Saito, M., Hirano, S., Uekama, Y., Iguchi, M., Takeshita, T., Mori, T.

Disaster Prevention Research Institute annuals Vol. 48 ( B ) page： 297 - 322 2005.4

Preliminary assessment of the waveform inversion method for interpretation of cross-well seismic data from the thermal production test, Mallik Gas Hydrate Production Research Well Reviewed

Watanabe, T., Shimizu, S., Asakawa, E., Kamei, R. and Matsuoka, T.

Scientific Results from Mallik 2000 Gas Hydrate Production Research Well Program, Mackenzie Delta, Northwest Territories, Canada, Geological Survey of Canada, Bulletin, Vol. 585 2005

Seismic Exploration Using Active Sources at Kuchierabujima Volcano, Southwest Japan Reviewed

Bulletin of the Earthquake Research Institute Vol. 80 ( 1 ) page： 11 - 40 2005

Differential waveform tomography for time-lapse crosswell seismic data with application to gas hydrate production monitoring Reviewed

Watanabe, T., Shimizu, S., Asakawa, E., Matsuoka, T.

Expanded Abstract of the 74th Annual Meeting, Society of Exploration Geophysicists page： TOM1.1 2004.10

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

To detect the change of physical properties in small areas, a series of high-resolution waveform inversions is applied to time-lapse seismic data. A procedure by use of ifferentiation between the time-lapse data and normalization using reference data is proposed in this study. The procedure is derived as a straightforward extension of waveform inversion as the scatterer imaging. Through numerical tests, the proposed approach was found to be more accurate than the conventional approach in obtaining the velocity change in small areas. The method was applied to the time-lapse crosswell seismic data obtained during the Mallik 2002 gas production test. A small area showing a velocity decrease near the production zone were found using the proposed method, indicating the existence of dissociated methane gas in the sand layers.

DOI： 10.1190/1.1845221

フルウェーブ・インバージョン Reviewed

渡辺俊樹

非破壊検査 Vol. 53 ( 5 ) page： 274 - 279 2004

人工地震を用いた富士山における構造探査

及川純, 鍵山恒臣, 田中聡, 宮町宏樹, 筒井智樹, 池田靖, 潟山弘明, 松尾のり道, 西村裕一, 山本圭吾, 渡辺俊樹, 大島弘光, 山崎文人

月刊地球 Vol. 号外No. 48 page： 23 - 26 2004

Viscoacoustic wave form inversion of transmission data for velocity and attenuation Reviewed

Watanabe, T., Nihei, K. T., Nakagawa, S., Myer, L. R.

Journal of Acoustical Society of America Vol. 115 ( 6 ) page： 3059-3067 2004

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

This study investigates the performance of a frequency domain viscoacoustic full waveform nonlinear inversion to obtain high resolution images of velocity and attenuation. An efficient frequency domain implementation is applied that consists of performing a series of single frequency inversions sweeping from low to high frequency. A cascaded inversion was adopted in which the real part of the velocity is first imaged using the phase information, then the quality factor (Q) is imaged using the amplitude information. Tests with synthetic data indicate that our approach yielded better images than the simultaneous determination of the real and imaginary part of the complex velocity. The method is applied to laboratory data obtained in a water tank with suspended acrylic bars. Broadband 200 kHz data is obtained for a crosshole configuration with a computer-controlled scanning system and piezofilm source and detector. The velocity image produced by the full waveform inversion is compared to a curved ray traveltime tomography velocity image, and was observed to possess higher resolution and more precise locations of the acrylic bars. The Q image shows a lower resolution than the velocity image, but recovers the correct Q for acrylic. This method can be applied for geophysical applications targeted to soil, unconsolidated rocks and marine sediments and also nondestructive evaluation and medical applications.

DOI： 10.1121/1.1710878

地震計アレイによる2.4km離れたACROSS震源からの弾性波の走時変動連続観測

雑賀敦, 山岡耕春, 國友孝洋, 渡辺俊樹

月刊地球 Vol. 号外No. 46 page： 105 - 112 2004

物理探査におけるアクティブ・モニタリング

渡辺俊樹

月刊地球 Vol. 号外No. 46 page： 166 - 172 2004

P-S converted seismic waves by a fracture and imaging Reviewed

Sanada, Y., Watanabe, T., Kiriyama, A., Ashida, Y.

ISRM 3rd Asian Rock Mechanics Symposium (ARMS) Vol. 1 page： 261 - 264 2004

周波数領域波形インバージョンによる孔間室内実験データの速度と減衰のイメージング Reviewed

渡辺俊樹, Nihei, K. T., Nakagawa, S. and Myer, L. R.

物理探査 Vol. 56 ( 2 ) page： 97 - 105 2003.6

Seismic imaging ahead of tunnel face with three-component geophones Reviewed

Ashida, Y., Matsuoka, T., Watanabe, T. and Kusumi, H.

Environmental Rock Engineering page： 371 - 375 2003

High resolution imaging of crosshole data using waveform inversion and reverse-time imaging Reviewed

Watanabe, T., Nihei, K. T., Nakagawa, S. and Myer, L. R.

Environmental Rock Engineering page： 317 - 322 2003

Simulation of Hopkinson effect by discrete element method Reviewed

Matsuoka, T., Kusumi, H., Ashida, Y. and Watanabe, T.

ISRM 2003 - Technology roadmap for rock mechanics - page： 813 - 816 2003

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