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SUMMARY Characteristics of the tsunami decay processes are examined following the definition and discussion of the major terms involved: 'moving root mean squared amplitude', 'tsunami coda' and 'non-dimensional tsunami amplitude' (NDA). Tsunami waveform data observed at tidal stations in Japan during two Kuril Island earthquake tsunamis in 2006 and 2007 are analysed. The tsunami codas of these events showed the following characteristics. (1) The decay process determined by the tsunami coda of the 2006 tsunami implies that the decay time constant at a tidal station depends on which ocean the station is facing. (2) Fluctuations of the NDAs in the tsunami codas are stochastically approximated by either the Rayleigh distribution or the normal distribution and the distributions of the NDAs at most tidal stations are similar. (3) Differences in the decay processes between these two tsunami events were small with regard to the averaged decay time constants and the distributions of the NDAs. These findings may be the first step towards improved forecasting of the tsunami decay process. [ABSTRACT FROM AUTHOR]

This paper presents post-tsunami survey results describing the impacts of the 2011 East Japan tsunami in Yos Sudarso Bay, Papua, Indonesia. Although the far-field tsunami had a height of 0.8 m measured at a tide gauge inside the small U-shaped bay, it severely damaged four villages scattered along the bay. Detailed numerical analysis was carried out to explain the damages. We used a well-verified source model in the near- and far-field cases to model the propagation of the tsunami southward in the Pacific until reaching Papua Island, Indonesia. The numerical analyses demonstrate two causes of damage in the bay: the maximum tsunami velocity (3.5 m s–1) floated the houses in the villages of Tobati and Enggros and caused them to collapse, and water trapped by the hook-shaped peninsula amplified the tsunami height at the Holtekamp and Hanurata. [ABSTRACT FROM AUTHOR]