Yui Nagahara

A Study on Characteristics of Harbor Vibration of Waves in Ports and Harbors in the Coastal Area of Niigata Prefecture

Naoyuki Inukai

 Ports in Niigata Prefecture support people's daily lives as a logistics hub. However, the Japan Sea is subject to high waves and tsunamis caused by winter winds and waves, which may cause damage to vessels and facilities.
 Therefore, in this study, numerical experiments and calculations were conducted to understand the effects of waves and tsunamis incident on ports and harbors in Niigata Prefecture. In addition, earthquakes that have occurred around Niigata Prefecture in the past were also investigated. The purpose of this study is to understand the conditions under which the water level increases in the ports and harbors in Niigata Prefecture, and to obtain knowledge for disaster prevention measures during emergency situations.
 First, simulations were conducted using NOWT-PARI for the present and future topography in response to the Niigata East Harbor Port road cave-in accident. As a result, it was found that the wave height reduction effect of the future topography is about 20% or more than that of the existing topography.
 Next, the observed tsunami period and heights were calculated for five ports where tsunamis were observed during the 2024 Noto Peninsula earthquake in Niigata Prefecture. The natural period and amplification factor of each port were also calculated using Merian's equation and a water level propagation model. From these results, the intrinsic period and the observed tsunami period were close to each other, and significant amplification factors were obtained for several ports.
 In addition, we conducted a survey of earthquakes that have caused tsunamis in Niigata Prefecture in the past. As a result, it was found that tsunamis with a period of about 30 minutes are likely to be observed in the vicinity of Niigata Prefecture. Therefore, it is important to pay attention to tsunamis with period around 30 minutes and intrinsic period, and to consider extending breakwaters.