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An Earthquake in Korea: A Look at the Gyeongju Earthquakes


By Christopher Hurst

As the residents of Gyeongju began cleaning up the damage caused by two powerful earthquakes earlier this month, a 4.5 magnitude aftershock struck on September 19. The tremors began on September 12 at 7:44 pm local time, when a 5.1 magnitude earthquake jolted Gyeongju. Less than an hour later there was a 5.8 magnitude quake, the largest in modern Korean history. This one was so powerful reports of shaking came from as far away as Busan and Daegu. While these events have been destructive and upsetting for the residents, there haven’t been any reported fatalities. Nevertheless, with so many earthquakes in such a short period, many have begun to question if the Korea peninsula is as safe from seismic activity as previously thought. Is there a reason for this rash of strong earthquakes in such a short time-frame? Moreover, is Korea prepared for a major earthquake?

Since 1978, Korea has only experienced five earthquakes that were 5.0 magnitude or greater. The earthquakes caused little damage, as the epicenters were offshore. However, small earthquakes (mostly undetectable by people on the ground) are happening in a greater number in recent years in Korea. Between 1978 and 1998, seismometers detected an average of 19.2 earthquakes per year on the peninsula. Since 1999, however that number has jumped up to 47.6 per year.

What is causing the increase in earthquakes? While Korea is not located on the “Pacific Rim of Fire” where many of the world’s earthquakes happen, they are near enough to feel some effects. Director Chi Heon-Cheol of the Earthquake Research Center under the Korea Institute of Geoscience and Mineral Resources (KIGMR) warned in April of this year that the recent seismic activity in the Kumamoto Prefecture in Japan could affect the potential for quakes in Korea, since the two share the same tectonic plate. A research team from Earth Observatory of Singapore also noted, “the on-going tectonic motions between the Philippine Sea plate and the Eurasian plate, as well as the tectonic deformation within northern China, are producing notable deformations in the peninsula, and reactivating the ancient fault in South Korea’s intraplate environment.” The news is not all gloom and doom, however. Many experts feel that while earthquakes may happen more frequently, Korea is still safe from the large earthquakes that Japan and Chile regularly face. A researcher at the KIGMR noted, “Although there can be earthquakes under 5.5 magnitude down the road, the overall geological structure in and around South Korea is not conducive to a major earthquake.”  For the moment, this seems to be true, as most of the aftershocks in the Gyeongju region have ranged in magnitude from 2.1 to 3.5.

With a potential increase in earthquakes on the horizon, many in Korea are starting to look at how prepared the country is. One of the biggest worries is that many of the nuclear power plants that provide almost one third of the power to the nation are located in the southeastern part of the country, the area most prone to earthquakes. Following the earthquakes, Korea Hydro and Nuclear Power Plant Company shut down the Wolsong power plant in Gyeongju as a precaution. Officials have stated that they are working to increase power plants ability to withstand earthquakes up to 7.0 on the Richter scale. All nuclear facilities can currently resist 6.5 magnitude earthquakes. Workers are expected to complete the upgrades by April 2018.

While officials feel that the nuclear power plants will soon be ready for future earthquakes, many of the high-rise apartments in Korea may not be. Korea adopted earthquake resistant structures and guidelines in 1988; however, enforcement has been loose. In 1998, Korea mandated earthquake resistance for buildings six stories or taller. However, there was no set standard in the law for builders to follow, causing concern for how powerful a quake they can resist. Currently, only 6.8 percent of the buildings in Korea today have earthquake resistant designs. In the face of worry from the public about the recent earthquakes, the government has quickly passed laws mandating earthquake resistance for all buildings as short as two stories and included defined requirements. President Park Geun-Hey has also promised to review and strengthen earthquake preparations for Korea. Hopefully, the events in Gyeongju will leave the country better prepared for when the next earthquake strikes.

Christopher Hurst is an intern at the Korea Economic Institute of America and a graduate of the University of Illinois at Chicago. The views expressed here are the author’s alone.

Photo from Adam Nicholson’s photostream on flickr Creative Commons.

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