Tsunami wave characteristics in Sendai Bay, Japan, following the 2016 Mw 6.9 Fukushima earthquake

On 21 November 2016, a Mw 6.9 intraplate earthquake occurred off the Fukushima coast in Japan, triggering a moderate-size tsunami with amplifications and long oscillations along the Sendai Bay coast. Here, we apply a hybrid approach to hindcast the wave characteristics in the Sendai Bay during the 2016 tsunami event, by analyzing coastal tide records, spectral analyses, and tsunami simulations. Our analysis shows that tsunami wave on tide stations mainly carried wave periods of 3.8-22.5 min, triggered by source periods of 18.5-22.5 min. The long oscillation in Sendai Bay was due to longer period of >28.8 min, affected by the presence of edge waves and oscillation of Sendai Bay. High-energy wave was found to be significant in most oscillation periods inside the Sendai Bay and around the Oshika Peninsula. The spatial distribution of maximum spectral and simulated tsunami amplitudes also reveal that the radiated tsunami energy was entrapped in the nearshore areas, resulting in resonance amplifications in the Sendai Bay.

Automated summary

This study analyzes the wave characteristics of a tsunami triggered by an intraplate earthquake in Japan's Fukushima coast in 2016. The analysis reveals that the tsunami wave consisted mainly of short wave periods but also exhibited long oscillations. High-energy waves were concentrated in the Sendai Bay and around the Oshika Peninsula. The analysis also indicates that the tsunami energy was entrapped in the nearshore areas, resulting in resonance amplifications in the Sendai Bay.