Tsunami hazard potential of submarine landslides in the southwestern East Sea (Sea of Japan)

Abstract

This study reveals that submarine landslides could pose a significant tsunami threat to the northeast (NE) coast of South Korea, with potentials of causing large damages and casualties. Recent bathymetric surveys identified four large submarine landslides (namely SL1 to SL4) at water depth ranging from 400 to 600 m in the southwestern East Sea (Sea of Japan), with volumes ranging between 2.1 and 4.4 km3. We evaluated tsunami potentials of these landslides with the COMCOT model. Numerical results show that these landslides, particularly SL3, could cause significant tsunami impact along the NE coast, with tsunami heights up to 8.0 m and current speeds up to 8.2 m/s at the coastline. Major cities along this coast, such as Gangneung and Donghae, are at risk of very short tsunami travel times (6–12 min) in all the simulated scenarios. The simulations also predict ~ 200 m inundation extent on land with flow depths of ~ 2 m in low-lying areas of coastal cities (e.g., Gangneung), indicating high potential of damages to buildings and infrastructure. We also examine major parameters that dominate the interaction between the submarine landslide and the resulting tsunami heights. Our analyses indicate that the rate of displaced volume of material with time, is closely linked to the steepness of the slip surface, significantly affects the tsunami heights. Additionally, comparisons with historical tsunami records on the NE coast of Korea suggest that local submarine landslides could cause much greater coastal impacts than the past, distant earthquake-triggered tsunamis. Our findings provide new insights into the understanding of tsunami hazards in the NE coast of Korea, as well as valuable information for tsunami education, exposure analysis, and mitigation planning in this region.