More tremors felt in recent years; geologists warn of greater seismic movements to come
September 22, 2016
Chang May Choon South Korea Correspondent In Seoul
Ms Lee Go Woon was having dinner with her family in the south-eastern port city of Busan when she felt the floor move, for about 30 seconds.
“I was quite surprised and didn’t know what to do because it was the first earthquake of my life,” said the assistant exhibition manager. “We never learnt how to deal with earthquakes because we always thought South Korea was safe from them.”
Ms Lee, 27, had two nights ago experienced an aftershock of South Korea’s biggest earthquake.
The 5.8-magnitude earthquake rocked most of the country on Sept 12, but did not cause any major damage. It was most strongly felt near the epicentre Gyeongju, a historical city in the south-eastern province of North Gyeongsang. Busan is 76km south-west of Gyeongju.
Fear is growing as aftershocks continue, and people are at a loss as to what to do. Some 400 aftershocks have been recorded, one of the latest being a magnitude 3.5 tremor that struck regions near Gyeongju around noon yesterday.
The Gyeongju earthquake is the most powerful to have hit the Korean Peninsula since records began in 1978. The last major seismic activity was a 5.3-magnitude earthquake that struck North Korea’s North Pyongan province in 1980.
South Korea has been relatively safe from major earthquakes, but geologists have expressed concern over the rising number of tremors felt in recent years and warned of bigger seismic movements to come.
The Korea Institute of Geoscience and Mineral Resources said last week that its studies show that a magnitude 6.5 quake could strike the Korean Peninsula in future. Some geologists predict that a quake with an even more powerful magnitude of 7.0 could strike the country.
Experts warned that powerful earthquakes could result in mass casualties as many buildings are not built to withstand them. The country is no stranger to gentle tremors of magnitude 2.0, but rarely experiences quakes of 5.0 or above.
To ease public anxiety, the government has held talks to discuss emergency quake-relief measures for the future. Yesterday, Prime Minister Hwang Kyo Ahn said they need to fix a budget to provide administrative support and allow the meteorological administration to send mobile alerts to the public effectively.
The Land Ministry announced on Tuesday more stringent control over earthquake-proof building designs starting next year, including additional safety evaluations for buildings 50 stories and taller.
Some experts noted that the Gyeongju earthquake was caused by activity in the Yangsan fault line in North Gyeongsang, while others said that recent earthquakes that shook Japan have shifted fault lines under the Korean Peninsula.
There are also rumours that the quake was triggered by North Korea’s latest nuclear test on Sept 9. But Dr Wang Yu, a research fellow at the Earth Observatory of Singapore, told The Straits Times it is “unlikely” that both events are related because the distance between them is vast.
Dr Wang said that aftershocks will “continue in the coming months to years”, but based on historical records, the chances of another damaging quake hitting Gyeongju is “relatively low”.
Some residents are not taking any chances. JoongAng Ilbo newspaper cited a Gyeongju resident who is making plans to move out of the city.
Another slept in her greenhouse because it was on flat land. The paper also quoted a father, in nearby Ulsan, who has been practising running down the stairs from his 19th-storey home with his six-month-old baby, as “it’s better than just sitting there stricken with fear”.
There are calls for the authorities to pay more attention to the safety of the country’s nuclear reactors, which are built to withstand earthquakes up to magnitude 7.0.
“We’re worried how long the aftershocks will last, and whether they are just teasers to a more severe earthquake,” Ms Lee said. “Koreans have been complacent about earthquakes so far, but now we need systemic control and manuals.”