under a Creative Commons License. Natural Hazards and Earth System Sciences Elastic oscillations of water column in the 2003 Tokachi-oki tsunami source: in-situ measurements and 3-D numerical modelling

Abstract. During the 2003 Tokachi-Oki tsunamigenic earth-quake the real-time JAMSTEC observatory obtained records which provided a unique opportunity to have a look deep in-side the tsunami source. Considering water column as a com-pressible medium we processed the bottom pressure records in order to estimate amplitude, duration and velocity of bot-tom displacement. Spectral analysis of the records revealed a clear manifestation of the low-frequency elastic oscillations of water column. We also presented 3-D finite-difference nu-merical model developed in the framework of linear poten-tial theory of ideal compressible fluid to better understand dynamical processes in the tsunami source. The model re-produces position of the main spectral maximum rather cor-rectly. However, due to neglecting of crust elasticity and to lack of exact knowledge of spatiotemporal laws of bottom motion, there is an essential difference between in-situ ob-served and computed spectra.