Warning from the East Sea - Earthquakes in Japanese Waters and Tsunami Risk to the Korean Peninsula

Introduction - The Background of the Question "Is the Korean Peninsula Safe?"

The question "Is the Korean Peninsula really safe?" is resurfacing. Concerns are being raised that the East Coast, which has been perceived as quiet and gentle, may actually be situated on a massive geological instability. This warning is amplified by an official report recently released by the Japanese government regarding the likelihood of a major earthquake along the East Sea coastline. The Japan Meteorological Agency reported that there is a 16-18% probability of a magnitude 7 or higher earthquake occurring within the next 30 years in the Chubu region of Honshu's western coast. This area, previously considered to have a relatively low risk for earthquakes, is now presenting a warning that contradicts existing beliefs. Earthquakes occurring in this region adjacent to the East Sea are not just a problem for Japan they have a high potential to directly impact the East Coast of the Korean Peninsula as well. Particularly, undersea earthquakes occurring in Japan are likely to be accompanied by tsunamis, which are a representative natural disaster that has significant effects on countries bordering the sea. The results of this investigation highlight the need to reevaluate perceptions of disaster risk on the Korean Peninsula.

Main Point 1 - Japan Earthquake Research Committee Announcement: Probability of a Major Earthquake within 30 Years is '16-18%'

The announcement from the Japanese Earthquake Investigation Committee is based on an analysis of 23 active fault lines in the area. This region spans from Hyogo Prefecture to Toyama Prefecture, located adjacent to the Sea of Japan. The assessment particularly focused on the distribution of "active fault zones," movement speed, ground structure, and the history of past earthquakes to evaluate the possibility of future seismic activity. Hirata Naoshi, the chairman of the Earthquake Investigation Committee and an emeritus professor at the University of Tokyo, stated that it is very unusual for areas to have an average probability exceeding 10%, and he emphasized that these are earthquake zones that must be closely monitored in the future. He also highlighted the potential for significant tsunamis in the event of an earthquake, advising nearby residents and the central government on the importance of preparedness. Analysis concluded that the Noto Peninsula region, which experienced a major earthquake last year, has reduced risk moving forward since that fault has already released considerable energy. However, other adjacent faults have emerged as new risk factors, increasing tension along the Sea of Japan coast. This announcement carries a message that cannot be overlooked by South Korea, facing the Sea of Japan, as it suggests that underwater earthquakes in Japan could impact the eastern coast of the Korean Peninsula with tsunamis and vibrations, considering geological continuity.

Main Point 2 - The East Coast of Korea, a Danger Zone, Not an Exception

The sense of crisis regarding earthquakes tends to be concentrated in countries along the Pacific Ring of Fire, such as Japan and Indonesia. However, recent geological studies are highlighting that South Korea's situation is far from exceptional. In particular, the east coast of the Korean Peninsula has ample potential to transform into a 'secondary damage area from tsunamis' caused by underwater earthquakes occurring in neighboring countries, even if it does not serve as a direct epicenter for earthquakes. A magnitude 7.7 earthquake that occurred in the seabed near western Japan in 1983 resulted in a tsunami crossing the East Sea and reaching Gangneung and Donghae in South Korea. Although the scale of damage at that time was not significant, this suggests the possibility of more severe damage developing at any time, depending on sea level conditions and the route of arrival. Recent domestic geological research is warning of another risk. According to a paper published in an international journal in April 2025, a scenario was suggested where 'submarine landslides' could occur in the deep seabed of the East Sea (at depths of 400-600m), potentially triggering a powerful tsunami. Submarine landslides are phenomena where underwater rocks or sediments suddenly collapse to create water columns, and they can occur independently of earthquakes, which necessitates even greater vigilance. According to this study, a tsunami could reach coastal cities such as Gangneung, Donghae, and Samcheok within 6 to 12 minutes after occurrence, with heights potentially reaching up to 8 meters, and flooding could extend more than 200 meters inland. This represents a duration and scale that current disaster response plans and warning systems would find very difficult to adequately address.

Main Body 3 - The Reality of the Alarm System and Response

Korea's disaster management system has been somewhat strengthened since the 2004 Indian Ocean earthquake, but it is often criticized for being overly focused on a warning system that prioritizes the Pacific coast. Specifically, the East Coast is perceived as an "indirectly affected area" rather than a "directly impacted area" for earthquakes and tsunamis, resulting in a relatively weak warning system and evacuation infrastructure. Actual cases of tsunami damage in Korea are few, leading to a low level of public awareness. However, experts have pointed to this as one of the most dangerous factors. Tsunamis can reach the coast within a few minutes, so if early warnings and immediate evacuations are not carried out, damages can escalate rapidly. Japan has systematically established tsunami evacuation signs and high-ground shelters along its coast, conducting regular training for residents. In contrast, while evacuation signs are often installed in tourist areas in Korea, practical education and training linked to the actual evacuation behavior of local residents and tourists are almost non-existent. This directly affects the speed of response and the scale of damage during disasters. Therefore, it is necessary to promptly design a tsunami warning system across the East Coast, secure evacuation routes, and establish region-specific training systems.

Conclusion - The 'stability' of the East Sea is in fact a latent 'danger'.

Until now, the East Sea has been considered a relatively quiet and stable maritime area. However, when comprehensively considering the announcement from the Japanese Earthquake Research Institute and geological studies at home and abroad, we reach the conclusion that the East Sea is by no means a safe zone. The geological structure extending beneath the sea transcends national borders, and earthquakes occurring in Japan may not be merely a Japanese issue. The East Sea is not only a geopolitical area connecting Korea, Japan, and Russia, but also a geological space that requires joint natural disaster monitoring and response. Therefore, it is time for Korea and Japan to strengthen cooperation in disaster information sharing, the joint development of tsunami monitoring systems, and marine disaster scenario simulations. Above all, the change in awareness within civil society is crucial. The complacency of thinking 'Surely it won't reach here?' can lead to great sacrifices in any disaster. Referring to Japan's risk assessment system and preparedness culture is important for us. Without accurate crisis recognition and preparation based on scientific data, no matter how modern a city is, it can become defenseless in the face of natural disasters. It is now necessary to adopt a strategic response of 'Prepared East Sea' instead of the perception of a 'Quiet East Sea.' The warnings of the East Sea are not simply predictions, but a realistic message urging immediate preparedness.