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Experts warn Pohang quake may be prelude to bigger tremors

All Headlines 20:48 November 15, 2017

SEOUL, Nov. 15 (Yonhap) -- South Korean officials and experts fear more earthquakes may occur for the next few months following the 5.4-magnitude tremor that struck the southeastern part of the country on Wednesday.

The earthquake took place some 9 kilometers from the coastal city of Pohang at 2:29 p.m.. At least 14 people were reported to have sustained light injuries as of 7 p.m.

It marked the second-strongest quake since the country began to collate seismic records in 1978. Korea's biggest magnitude 5.8 earthquake hit Gyeongju, near Pohang, last year.

Experts attributed the latest quake to the displacement of a fault active in the country's southeastern region, although they said it's too early to determine the cause and further study is needed based on data analysis.

"When 5-magnitude or more powerful earthquakes occur, large and small aftershocks usually continue for months. A few aftershocks will follow this time too," Lee Mi-sun, a Korea Meteorological Administration (KMA) official in charge of seismic and volcanic affairs, told reporters.

The agency is looking into the possibility that the latest quake may have been caused by the activities of an eastern branch of Yangsan Fault, the most prominent fault plane in the southeastern part of the Korean Peninsula. Experts linked the Gyeongju quake to the 170-km fault line and its southern branch.

She also said the agency is also considering geologists' suggestion that the southeastern fault lines of the peninsula were destabilized by the 9-magnitude earthquake which hit northeastern Japan in 2011.

An expert suggested that the latest quake may be a prelude to more powerful ones to occur in the coming days, citing precedents in Korea and Japan.

"Gyeongju was struck with a bigger quake a week after a slightly less powerful quake (5.1 magnitude) had hit the region," said Sohn Moon, a professor of geology and environmental science at Pusan National University.
He said the quake may have been triggered by ruptures in the Yangsan fault plane and that means this quake may only be a prelude to larger-scale tremors.

Sohn also cited a 7.4-magnitude earthquake that occurred in Kumamoto, Japan, which came days after a 7.1-magnitude quake struck the area.

Hong Tae-kyung, an earth science professor at Yonsei University, noted there are not many known active faults below the Pohang area. He calls for more analysis raising the possibility that there may be unknown fault lines.

They also stressed the need for caution and called for stepped-up efforts in case of any possible quakes that could come with a bigger impact.

"We need to prepare for the possibility of a quake of 7 magnitude or higher, and bolster efforts to have more quake-resistant buildings and facilities around us."


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