Abstract
In the present study, the local tsunami amplification observed in Ryori Bay, located on the Sanriku coast of Japan, was investigated using numerical simulations. Large-scale tsunami propagation simulations and tsunami inundation simulations for the bay were systematically conducted to estimate and model the 2011, 1933, and 1896 tsunamis that occurred off the Sanriku coast and which resulted in large run-ups. The simulation results, which are moderately consistent with observations, presented larger run-up heights and inundations for the 1933 and 1896 tsunamis (which followed relatively small earthquakes) compared to those of the 2011 tsunami (which followed a larger earthquake). Furthermore, the frequency analysis indicated that the former two tsunamis comprised higher predominant components. A tsunami inundation simulation using parametrized synthetic waveforms was conducted to identify the contributing factors associated with the large amplification and run-ups. The results indicated that the predominant components are significantly amplified in the bay and the initial decrease in the water surface elevation prior to the primary waves of the two tsunamis leads to an increase in their run-up heights. Furthermore, the simulated waveforms of the tsunamis revealed that the 1933 and 1896 tsunamis had their wavefronts changed into a steep wavefront, i.e., a bore-like wave, during their wave developments in the bay, attributed to shoaling, narrowing bay width, and the nonlinear effect of the wave. These results, therefore, indicate that bores which are known to generate large run-up heights were generated in the bay during the two tsunamis.
Highlights
Located in the Tohoku region and facing the Pacific Ocean, the Sanriku coast of Iwate Prefecture in Japan has experienced large tsunami disasters due to earthquakes that have occurred in the vicinity of the Japan Trench
Wei et al (2013) estimated the tsunami inundation based on a source model that was developed by the National Oceanic and Atmospheric Administration within 1.5 h of the Yamanaka and Nakamura Earth, Planets and Space (2020) 72:6
Concluding remarks In the present study, the 2011 Tohoku, the 1933 Sanriku, and the 1896 Sanriku tsunamis propagating into Ryori Bay were investigated using numerical simulations to estimate the nearshore behaviors including inundation and run-up
Summary
Located in the Tohoku region and facing the Pacific Ocean, the Sanriku coast of Iwate Prefecture in Japan has experienced large tsunami disasters due to earthquakes that have occurred in the vicinity of the Japan Trench. The estimated moment magnitude of the earthquake, Mw, was 9.1 according to the Global Centroid–Moment–Tensor (CMT) Catalogue (Dziewonski and Anderson 1981; Ekström et al 2012). This earthquake caused a catastrophic tsunami that resulted in over 15,000 deaths (Mori et al 2011). Satake et al (2013) developed an earthquake source model that has a length of 500 km and a width of 200 km and is based on a waveform inversion technique using the observed tsunami waveforms (Fig. 1a). Wei et al (2013) estimated the tsunami inundation based on a source model that was developed by the National Oceanic and Atmospheric Administration within 1.5 h of the Yamanaka and Nakamura Earth, Planets and Space (2020) 72:6
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