The Korean Peninsula is Not 'Stable'

Professor Kim Gi-beom explained that the fundamental cause of earthquakes on the Korean Peninsula lies in the collision of the Pacific Plate and the Philippine Sea Plate. The Pacific Plate collides with Japan at a speed of 8 cm per year, and the Philippine Sea Plate at 4-5 cm per year, generating immense energy. This collision energy propagates along the Japanese archipelago, causing crustal deformation in areas far from the collision points, such as Kumamoto and the Noto Peninsula. Professor Kim pointed out that the Korean Peninsula is not free from the aftershocks of these plate collisions.

The Noto Peninsula earthquake that occurred in 2024 took place 600 km away from the collision point. This is an example showing that collision energy can propagate far along the Median Tectonic Line and the Dolgorae-Sanin Shear Zone. Professor Kim emphasized that it is important to note that earthquake energy can be transmitted over such a wide range, causing a powerful earthquake of magnitude 7.6.

This linkage is also confirmed in past earthquake cases. Professor Kim Gi-beom mentioned that after a magnitude 7.3 earthquake occurred in Kumamoto in April 2016, a magnitude 5 earthquake occurred off the coast of Ulsan three months later, followed by a magnitude 5.8 earthquake in Gyeongju two months after that. This case suggests the existence of a causal system for earthquake occurrences on a broad scale, indicating that the Korean Peninsula cannot escape the after-effects of major earthquakes in Japan.

Seismic energy originating from the Dolgorae-Sanin Shear Zone connects to Busan via Tsushima, affecting major fault zones in the interior of the Korean Peninsula. Professor Kim Gi-beom explained that the Yangsan Fault Zone, where the Pohang, Ulsan, and Gyeongju earthquakes occurred, and the Ulleung Fault Zone on the east coast, are also affected by the collision energy of the Pacific Plate and the Philippine Sea Plate. This means that internal faults on the Korean Peninsula are not unrelated to the movements of external plates.

Professor Kim Gi-beom revealed through his research published in American academic journals in 2018 and 2023 that the East Sea subduction phenomenon is occurring not only on the Japanese side but also on the Korean Peninsula side. This phenomenon is called the 'Ulleung Fault' and showed a pattern where actual earthquake records matched the fault's location. This suggests that crustal activity in the waters around the Korean Peninsula is more active than expected, increasing the likelihood of earthquakes.

Professor Kim Gi-beom emphasized the earthquake history of the Korean Peninsula through records of major earthquakes in the Annals of the Joseon Dynasty. Records of the 1643 Ulsan Great Earthquake and the 1681 Yangyang Great Earthquake describe phenomena such as city walls collapsing, water boiling, and tsunami-like events in the sea. Specifically, during the Yangyang earthquake, there is a concrete record that the coastline receded by about 150m. These past records clearly show that the Korean Peninsula experienced large-scale earthquakes and consequent coastline changes.

Coastline changes due to earthquakes are also observed in modern earthquakes. Professor Kim Gi-beom mentioned the case of the Noto Peninsula earthquake in Japan, where the ground uplifted by up to 4m, causing the coastline to recede by about 150-200m. This fact has been proven by academic papers such as Scientific Reports, showing that a single earthquake can turn what was once sea into land. This phenomenon supports the fact that the records in the Annals of the Joseon Dynasty were by no means exaggerations.

Past earthquakes recorded in the Annals of the Joseon Dynasty are presumed to have been similar in magnitude to modern earthquakes. Professor Kim Gi-beom warned that if a magnitude 7.6 earthquake occurs off the coast of Korea, it could cause significant damage, similar to the Noto Peninsula earthquake. Indeed, there are records of an earthquake estimated at magnitude 6.8 in Suncheon, South Jeolla Province, in the second year of King Danjong (1454), and an earthquake estimated at magnitude 5.7-6.4 in Jangheung, South Jeolla Province, in the 13th year of King Hyeonjong (1672). This is evidence that the Korean Peninsula was vulnerable to large-scale earthquakes in the past.

Professor Kim Gi-beom pointed out that judging the seismic safety of the Korean Peninsula based solely on short-term observation data from the last 20-30 years is very dangerous. He cited the examples of the Nankai Trough (130-year cycle) and the Japan Trench (400-year cycle), emphasizing that earthquakes have long-term characteristics and therefore past records should be examined from a diachronic perspective. He particularly stressed that neglecting the major earthquake records in the Annals of the Joseon Dynasty and responding complacently should be avoided, and long-term earthquake prevention and disaster preparedness measures should be established.

Professor Kim Gi-beom criticized the complacent attitude of earthquake prediction and disaster prevention officials who overlook past records and urged them to awaken. He emphasized that based on the major earthquake records remaining in the Annals of the Joseon Dynasty, the possibility of earthquakes of magnitude 5 or higher occurring on the Korean Peninsula should never be ruled out. He argued that practical earthquake countermeasures should be established by thoroughly reviewing the damage cases remaining in the records.

Regarding the possibility of a Baekdusan eruption, Professor Kim Gi-beom believed that an eruption could occur at any time. He explained that there is always a possibility of eruption on a 100-year cycle, and small-scale eruptions, such as the Kagoshima Sakurajima volcano case, can occur routinely. However, large-scale eruptions like the millennium-ago grand eruption that occurred in 946 AD are analyzed to have a cycle of about 50,000 years, so the possibility of a large-scale eruption occurring in the short term is low.

Professor Kim Gi-beom pointed out serious problems with Korea's earthquake response system. He criticized the reality that specific information about which fault caused an earthquake is not immediately reported when it occurs. While overseas organizations like the US USGS provide analysis of fault movement direction and mechanism immediately after an earthquake, the Korea Meteorological Administration fails to provide such information due to a lack of internal analysis experts and personnel. This makes effective response difficult as rapid and accurate information is not provided during an earthquake.

Professor Kim Gi-beom emphasized the importance of 'Focal Mechanism Solution' analysis technology, which analyzes not only the depth, latitude, and longitude of an earthquake but also the type of slip that caused it. He criticized that while a beachball diagram can interpret the direction of fault slip, there is almost no system or infrastructure for such earthquake analysis in Korea. He asserted that such experts should be equipped in disaster response and prediction agencies.

Korea's active fault investigation only began after the Gyeongju earthquake in 2016. Professor Kim Gi-beom pointed out that information on active faults that had moved within the last 10,000 years was almost non-existent before then. He explained that before the Gyeongju earthquake, Korea was perceived as a stable intraplate environment, so there was little awareness of active fault investigation. This can be seen as a result of overlooking past earthquake records.

Professor Kim Gi-beom strongly argued that the perception of Korea being in a 'stable intraplate environment' must be abandoned. He emphasized that Korea is located very close to the Pacific Ring of Fire, and unconsumed collision energy from the trench propagates into Korea. He added that Korea is only about 500 km away from the Nankai Trough, making it clear that the Korean Peninsula is by no means a seismically safe zone.

Professor Kim Gi-beom mentioned the possibility that the Amur Plate boundary passes through Korea. Japanese academia already recognizes the western coast of Japan as the boundary of the Amur Plate, and there is also a view that the East Sea is a subduction zone that is a plate boundary. Various research results suggest that the western boundary of the Amur Plate passes through the west coast or penetrates the Korean Peninsula, leading to differing interpretations of the boundary's location among scholars. These studies suggest that the Korean Peninsula may be adjacent to a plate boundary with earthquake potential.