Gyeongju in 2016, a 6.8 percent share, and a 1988 law

After the September 2016 Gyeongju earthquake — the largest, the notes write, in Korea’s instrumental record — smaller shocks kept coming, and a worry spread that the country was not a safe zone after all. Intraplate events such as the Sichuan earthquake, they add, have been growing more frequent, so a large shock in Korea cannot be ruled out. A related seismic law had been in place since 1988, they write, and seismic design has been applied since then, but the share of domestic buildings with that design was, in their figure, only 6.8 percent, a stock they call very vulnerable.

Urbanization over the previous half-century, they write, had also raised the risk inside cities. A damage-prediction model from the Ministry of Public Safety and Security, as they cite it, put the building losses in Seoul from a magnitude 7.0 shock at 427 trillion won, and indirect losses at 536 trillion won. Anxiety, they say, was growing, and the government was tightening seismic design rules as part of disaster prevention, while also pushing the retrofit of existing public facilities. Those official figures and that tightening stay in the notes’ own window, not as later totals.

Which buildings the rules pick out

The aim of Korea’s seismic design, the notes write, is to secure the seismic performance of a structure’s foundation, and to keep foundation damage and the economic loss that follows as small as possible. The domestic standard, they say, follows foundation seismic-design criteria. Under Article 32(2) of the Enforcement Decree of the Building Act, an owner of a building in any of the listed categories must receive a structural-safety confirmation from the designer and submit it to the permitting authority when filing the commencement report under Article 21.

Among the buildings they list as needing seismic design are wood structures of three stories or more — warehouses, livestock sheds, crop houses, and buildings from standard design books excepted — and wood buildings of 500 square meters or more; buildings 13 meters or taller, or with eaves 9 meters or taller; buildings with 10 meters or more between columns; buildings of high importance designated by ordinance of the Ministry of Land, Infrastructure and Transport; nationally valuable heritage structures; buildings with a beam or awning fixed at one end and projecting 3 meters or more from the center line of an exterior wall, or other special methods the minister announces; and, last, detached houses and multi-family houses under the attached table.

After Pohang in 2017, how a window should be detailed

The 2017 Pohang shock, the notes write, damaged buildings without seismic design one after another, and brought the need for that design back into view. Poor original design or shoddy work, they say, meant seismic windows had not been installed properly, so sashes shook and broke, or fell and injured people below. If glass is made without a gap, so that it touches the building, it breaks easily. Windows packed along the south side for light and air, they add, also concentrate the damage, so it is better to reduce the size and number of openings, and a full-width front window needs especially careful design.

A corner window takes lateral force in a quake, and the corner is the weakest point, so a shear wall should be kept between the two openings. Irregular, asymmetric layouts should be avoided, so that when a lateral load arrives it is shared evenly. To keep a sash from shaking loose or twisting, the shock itself has to be eased. For buildings already up, they describe a method that does not alter the wall: a rectangular frame, or a pi-shaped frame open at the bottom, with a horizontal stiffener fitted to the outer face of the horizontal member, and an L-shaped corner piece holding that stiffener to the vertical frame. The same Korean report, at fuller length, is on CampusDown.

Sources

1. The notes’ account of seismic design in Korea, including the 6.8 percent share, the 2016 Gyeongju and 2017 Pohang shocks, and window detailing

Last updated: 14 November 2026