On the morning of June 12, a 4.8 magnitude earthquake struck Buan, North Jeolla Province, the largest of the year. A strong earthquake occurred in an area where earthquakes were not frequent, and shaking was felt not only in nearby areas but also across the country, including the Seoul metropolitan area and the southeastern region. The Korea Meteorological Administration (KMA) said the 4.8 magnitude earthquake struck 4 kilometers south-southwest of Buan-gun, North Jeolla Province at 8:26:49 a.m. The epicenter is 35.70 degrees north latitude and 126.71 degrees east longitude. The administrative district of the epicenter is Jindong-ri, Haengan-myeon, Buan-gun, and its depth is estimated to be 8 kilometers. This is the largest earthquake to hit the Korean Peninsula and surrounding waters this year.

Initially, the KMA estimated the magnitude of the earthquake to be 4.7 based on the results of an automated analysis of P waves, which are the fastest seismic waves, but raised it to 4.8 after further analysis.

There were 17 aftershocks by 6 p.m. that day. The largest of the aftershocks was a magnitude 3.1 earthquake that struck 4 kilometers south of Buan-gun at around 1:55 p.m. The remaining 14 aftershocks were all small, with magnitudes of 2.0 or less. Earthquakes with a magnitude of 2.0 or less are often not felt by most people.

The earthquake was felt in the southwestern region of Korea, centered on Buan, as well as in the Seoul metropolitan area, Chungcheong Province, and the southeastern region.

North Jeolla Province was estimated to have a maximum instrumental magnitude of 5, while South Jeolla Province had a magnitude of 4. A magnitude of 5 means the degree to which almost everyone feels vibration, bowls, windows, etc. are broken, and unstable objects fall. A magnitude of 4 is felt by many people indoors, and at night, they wake up, and bowls and windows shake. In addition, Gyeongsang Province, Gwangju, Daejeon, Sejong, Incheon, and Chungcheong Province were estimated to have an instrumental magnitude of 3. The KMA and fire authorities said they had received a total of 309 reports of shaking across the country by 10:30 a.m., about two hours after the earthquake. There were also reports of tremors in Wonju, Gangwon Province, which is 300 kilometers from Buan-gun.

In terms of scale, the earthquake, which was recorded as the largest this year, is the 16th since 1978 when the KMA began observing earthquakes with instruments. It is the 12th largest since 1999 when it began digital observation. The earthquake was characterized by its occurrence in North Jeolla Province where strong earthquakes were rare. Within a radius of 50 kilometers of the earthquake, there have only been 10 earthquakes with a magnitude of 3.0 or higher since 1978. This is the first time a magnitude 4.0 or higher earthquake has occurred in the region.

The government operated the first stage of the Central Disaster and Safety Countermeasures Headquarters’ emergency measures and began responding to the situation. Korea Hydro & Nuclear Power said, "All nuclear power plants operating nationwide are operating safely without any impact from the earthquake."