RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 12, ES2005, doi:10.2205/2011ES000509, 2011

Hydroacoustic effects in the 2003 Tokachi-oki tsunami source

¹Faculty of Physics, M. V. Lomonosov Moscow State University, Russia

²Engineering Seismology Section, Takenaka Research & Development Institute, Tokyo, Japan

³Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan

⁴Japan Dam Engineering Center, Tokyo, Japan

Abstract

We process the JAMSTEC ocean-bottom pressure gauges and ocean-bottom seismometers datasets obtained during the 2003 Tokachi-oki tsunamigenic earthquake – the first records which have ever been obtained in a large tsunami source. On these records, we discover the unique phenomenon in tsunami source – hydroacoustic resonance, i.e. manifestation of long-lasting elastic oscillations of water column at the minimal normal frequency (~0.14 Hz). The concept of a weakly coupled system is applied in 3D numerical simulation of the Tokachi-oki event. First, we simulate earthquake ground motion due to seismic fault rupturing. Then, compressible water column disturbance resulting from the dynamic seismic ground motion is simulated using the velocity of bottom deformation as an input to the water column. Comparison between JAMSTEC in-situ measurements and synthetic signals is carried out.

Received 21 November 2011; accepted 28 November 2011; published 10 December 2011.

Keywords: Tsunami source; bottom earthquake; water compressibility; dynamic bottom deformation; numerical simulation; ocean-bottom pressure gauges; ocean-bottom seismometers; spectrograms

Citation: Bolshakova A., S. Inoue, S. Kolesov, H. Matsumoto, M. Nosov, T. Ohmachi (2011), Hydroacoustic effects in the 2003 Tokachi-oki tsunami source, Russ. J. Earth Sci., 12, ES2005, doi:10.2205/2011ES000509.