Locally amplified tsunami in Iida Bay due to the 2024 Noto Peninsula Earthquake

The 2024 Noto Peninsula Earthquake in Japan generated tsunamis of over 3 m high in Iida Bay, causing extensive damage to ports and residential areas. The tsunamis observed in Iida Bay were remarkably higher than those at other coasts, and it can be inferred that some mechanisms may have amplified the tsunami. This study aimed to elucidate why tsunami damage was concentrated in Iida Bay. A numerical simulation showed that the tsunami energy propagating from the earthquake source fault toward Toyama Bay converged on the edge between the shallow sea (Iida Spur) and the deep sea (Toyama Trough). The concentrated tsunami energy then propagated into Iida Bay, triggering multiple secondary short-period tsunamis. According to video monitoring overlooking Iida Bay, a bore-like tsunami propagating along the coastline intersected with a tsunami directly reaching Iida Port, resulting in an over 10-m high splash when it hit the breakwater. Wavelet analysis of the computational output showed that the primary tsunami energy had an oscillation period of 5–10 min, whereas that of the secondary tsunami energy was less than 2 min. The superposition of these multiple waves most likely caused the locally amplified tsunami in Iida Bay.