Dynamic Response of Bottom Water Pressure due to the 2011 Tohoku Earthquake
Hiroyuki Matsumoto*, Shusaku Inoue**, and Tatsuo Ohmachi***
*Japan Agency for Marin-Earth Science and Technology, 2-15 Natsushima, Yokosuka 237-0061, Japan
**Takenaka Research and Development Institute, 1-5-1 Ohtsuka, Inzai, Chiba 270-1395, Japan
***Japan Dam Engineering Center, Nissyoku Bld., 2-9-7 Ikenohata, Taito, Tokyo 110-0008, Japan
Water pressure changes have been recorded during the 2011 Tohoku earthquake (Mw9.0) by two oceanbottom pressure gauges of the JAMSTEC cabled observatory located approximately 400 km north of the tsunami source. In the present study, observed water pressure fluctuations have been interpreted by timefrequency processing analysis, followed by a comparison with those fluctuations of ocean-bottomseismometers. Acoustic resonance has been involved due to seismic waves even in the intermediate-field. The present study suggests that water pressure fluctuations during the 2011 Tohoku earthquake are dominated by oceanbottom acceleration and velocity for the intermediate frequency range and the high-frequency range, respectively, and its threshold roughly coincides with the fundamental acoustic resonant frequency. Water pressure amplitude is independent, in contrast, on bottom oscillations in the low-frequency range, for which the threshold is related to intermediate waves rather than shallow water waves.
-  Y. Hayashi, H. Tsushima, K. Hirata, K. Kimura, and K. Maeda, “Tsunami source area of the 2011 off the Pacific coast of Tohoku Earthquake determined from tsunami arrival times at offshore observation stations,” Earth Plants Space, Vol.63, pp. 809-813, 2011.
-  T. Ozaki, “Outline of the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0) – Tsunami warnings/advisories and observations –,” Earth Plants Space, Vol.63, pp. 827-830, 2011.
-  T. Maeda, T. Furumura, S. Sakai, and M. Shinohara, “Significant tsunami observed at ocean-bottom pressure gauges during the 2011 off the Pacific coast of Tohoku Earthquake,” Earth Plants Space, Vol.63, pp. 803-808, 2011.
-  K. Hirata, M. Aoyagi, H. Mikada, K. Kawaguchi, Y. Kaiho, R. Iwase, S. Morita, I. Fujisawa, H. Sugioka, K. Mitsuzawa, K. Suyehiro, H. Kinoshita, and N. Fujiwara, “Real-time geophysical measurements on the deep seafloor using submarine cable in the southern Kurile subduction zone,” IEEE J. Ocean. Eng., Vol.27, pp. 170-181, 2002.
-  U. S. Geological Survey, “Finite fault model, Updated result of the Mar 11, 2011 Mw9.0 earthquake offshore Honshu, Japan,” 2011.
http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usc0001xgp/finite_fault.php [accessed at 27 December, 2011]
-  Y. Fujii, K. Satake, S. Sakai, M. Shinohara, and T. Kanazawa, “Tsunami source of the 2011 off the pacific coast of Tohoku Earthquake,” Earth Plants Space, Vol.63, pp. 815-820, 2011.
-  M. Takahashi, “Telemetry bottom pressure observation system at a depth of 2,200 meter,” J. Phys. Earth, Vol.29, pp. 77-88, 1981.
-  M. Nosov and S. Kolesov, “Elastic oscillations of water column in the 2003 Tokachi-oki tsunami source: in-situ measurements and 3-D numerical modeling,” Nat. Haz. Earth Sys. Sci., Vol.7, pp. 243-249, 2007.
-  K. Takayama, “Statistical relationship between tsunami maximum amplitudes of offshore and coastal stations,” Pap. Meteorol. Geophys., Vol.59, pp. 83-95, 2008 (in Japanese with English abstract).
-  A. Bolshakova, S. Inoue, S. Kolesov, H. Matsumoto, M. Nosov, and T. Ohmachi, “Hydroacoustic effects in the 2003 Tokachi-oki tsunami source,” Russ. J. Earth. Sci., Vol.12, ES2005, 2011. doi:10.2205/2011ES000509
-  A. Bergant, A. R. Simpson, and A. S. Tijsseling, “Water hammer with column separation: A historical review,” J. Fluids Structures, 22, pp. 135-177, 2006.
-  T. B. Benjamin and F. Ursell, “The stability of the plane free surface of a liquid in vertical periodic motion,” Proc. R. Soc. London, 255, 505, 1954.
-  J. H. Filloux, “Tsunami record on the open ocean floor,” Geophys. Res. Lett., Vol.9, pp. 25-28, 1982.