A parameter quantifying radiation damping of bay oscillations excited by incident tsunamis. (1st April 2018)

• Record Type: Journal Article
• Authors: Endoh, Takahiro; Inazu, Daisuke; Waseda, Takuji; Hibiya, Toshiyuki
• Is Part Of: Continental shelf research. Volume 157(2018)
• Page Start: 10
• Page End: 19
• Publication Date: 2018-04-01
• Subjects: Tsunami -- Harbor oscillation -- Resonance -- Radiation damping -- Quality factor -- Transient response -- Linear time-invariant system; Continental shelf -- Periodicals; Submarine geology -- Periodicals; 551.41
• DOI: 10.1016/j.csr.2018.02.007
• Languages: English
• ISSNs: 0278-4343

Abstract

Abstract: The transient response of a bay with a narrow mouth to incident tsunamis is interpreted as the convolution of the input signal with the impulse response obtained by an inverse Fourier transform of the response curve of the oscillatory system with one degree of freedom. The rate of radiation damping associated with energy escaping seaward through the bay mouth is expressed in terms of the quality factor Q, which determines the decaying envelope of the impulse response. The value of Q of the resonant peak is approximated by the ratio of the resonant frequency ω 0 to the bandwidth between frequencies at which the power spectral density of sea level within the bay drops to half of the peak value. Since the shape of the frequency power spectrum during the tsunami event is almost similar to that in the normal state in the neighborhood of ω 0, Q can be estimated from sea level datasets in the normal state. Although the amplitude and phase of the impulse response need to be adjusted using the first crest or trough of the observed leading wave, this approach proves to work well in examining the transient responses of Miyako Bay and Kushimoto Bay on the Japanese Pacific coast to incident tsunamis. Highlights: The response of the narrow mouthed bay to tsunamis is quantified by the quality factor Q. Q is the measure of radiation damping associated with energy escaping seaward. The value of Q can be estimated from sea level datasets in the normal state.