INVESTIGATION OF TSUNAMI INDUCED HARBOR OSCILATIONS ALONG THE NIIGATA COASTLINE AT THE NOTO PENINSULA EARTHQUAKE

Abstract

 The tsunami generated by the 2024 Noto Peninsula Earthquake reached the coastal region of Niigata Prefecture, where it was observed at several ports including Naoetsu Port. Upon tsunami arrival, resonant phenomena—such as phase differences and amplification of wave heights—occurred more prominently inside the ports than offshore. This study aims to elucidate the tsunami response characteristics of ports in Niigata Prefecture resulting from the Noto Peninsula Earthquake and to identify the resonance conditions for tsunamis in these ports by investigating the periods of past tsunami events.

 First, the periods and wave heights of the observed tsunamis were calculated using data collected from both inside and outside the affected ports. Then, the natural periods up to the third mode and the amplification factors of each port were estimated using analytical formulas. Furthermore, numerical simulations were conducted to assess water level fluctuations within the ports during tsunami arrival. By varying the input tsunami periods in the simulations, the resonance characteristics and amplification behaviors of each port were evaluated.

 Finally, the relationship between the source regions of past tsunamis and the tsunami periods upon reaching the Niigata coastline was analyzed. Based on this, the tsunami source areas and periods most likely to induce resonance at each port in Niigata Prefecture were identified, and potential mitigation strategies were discussed.