KMA: "Aftershocks in Jeju May Continue for Months... No Tsunami Risk" (Comprehensive)

Magnitude 4.9 Earthquake Occurs Southwest of Seogwipo, Jeju
Reports of Tile Separation and Broken Windows
"Additional Research Needed on Links to Japanese Earthquakes and Volcanoes"
No Tsunami Risk Expected

The Korea Meteorological Administration's National Earthquake and Volcano Situation Room is responding to the occurrence of a magnitude 4.9 earthquake in Jeju on the afternoon of the 14th.

[Asia Economy Reporter Han Jinju] After a magnitude 4.9 earthquake occurred on the 14th in the sea area southwest of Seogwipo, Jeju, it is expected that aftershocks could continue for several months.

At an emergency briefing held by the Korea Meteorological Administration (KMA) on the 14th, Yu Sang-jin, head of the Earthquake and Volcano Policy Division, stated, "Aftershocks can occur for several months up to a year after the earthquake, so continuous monitoring and response are necessary."

According to the KMA, a total of nine aftershocks occurred by 7:30 p.m. that day. At the Jeju Typhoon Center, buildings shook for about two seconds accompanied by a 'thud' sound, and buildings also shook at the KMA Jeju office and Seogwipo observation station.

According to the Fire Agency's tally, as of 9 p.m., a total of 169 earthquake detection reports were received: 110 in Jeju, 37 in Jeonnam, and 6 in Daejeon.

Damage assessments are ongoing in various locations. As of 9 p.m., the Fire Agency received three earthquake damage reports. In an apartment in Ido 1-dong, Jeju, veranda tiles separated; in Yeondong, windows of a row house were broken; and in the kitchen of an apartment in Sehwa-ri, Gujwa-eup, a report was received that the floor had tilted.

Regarding why the damage was less than that of the Pohang and Gyeongju earthquakes, Yu explained, "Earthquake damage is influenced more by the seismic intensity, which is the degree of shaking as the earthquake moves, rather than the absolute magnitude." He added, "The maximum seismic intensity in Jeju reached 5, which meant most people indoors felt it, and windows could break or unstable objects could fall." The instrumental intensities for this earthquake were 5 in Jeju, 3 in Jeonnam, and 2 in Gyeongnam, Gwangju, and Jeonbuk.

Although the earthquake occurred offshore, the KMA explained that there is no possibility of a tsunami. Yu said, "This earthquake was magnitude 4.9 with strike-slip fault movement, so it does not have enough energy to generate a tsunami." He added, "Tsunamis pose a risk when a certain level of energy is released by reverse or normal faulting."

Regarding the relation to recent consecutive earthquakes or volcanic activity in Japan, Yu said, "It is difficult to assert definitively, and further investigation and research are needed." He continued, "Earthquakes occur as stress accumulates and releases, so they can be directly or indirectly influenced by nearby earthquakes."

This earthquake was caused by strike-slip fault movement, which mainly occurs in the southern and western sea areas around the Korean Peninsula. The fault movement direction is north-south or east-west, and the moment magnitude (calculated by interpreting the fault movement that caused the earthquake) is 4.8.

This earthquake is the joint 11th largest since seismic observations began in 1978. The largest earthquake on record was a magnitude 5.8 earthquake that occurred 8.7 km south-southwest of Gyeongju, Gyeongbuk, in September 2016. The next largest was a magnitude 5.4 earthquake that occurred 8 km north of Buk-gu, Pohang, Gyeongbuk, on November 15, 2017.

This is the largest earthquake to occur in Jeju. The largest earthquake within a 50 km radius of the epicenter was a magnitude 3.9 earthquake that occurred in the sea area 26 km south of Gosan, Jeju City, at 7 a.m. on June 15, 2005.

This earthquake occurred at 5:19:14 p.m. on the same day in the sea area 41 km southwest of Seogwipo, Jeju. The epicenter is at 33.09°N latitude and 126.16°E longitude. The depth was 17 km. The initially analyzed magnitude at the time of first observation was 5.3, but based on manually analyzed data, the magnitude was revised downward to 4.9. The initial observation time refers to the time when the fast-moving P-wave arrived.

This content was produced with the assistance of AI translation services.