North Korea’s latest nuclear test Sunday, which is presumed to be the most powerful of all conducted by the communist regime so far, sent tremors to South Korea, about 500 kilometers away from the explosion.

The test was conducted at the North’s nuclear test site of Punggye-ri, some 460 kilometers from the South’s capital Seoul, at around 12:30 p.m., the South Korean Meteorological Administration said. It caused an artificial earthquake of magnitude 5.7. The US Geological Survey put the level of seismic activity at 6.3. North Korea claimed later Sunday that it was a hydrogen bomb to be fitted onto an intercontinental ballistic missile, calling the test a “perfect success.”
 
“The earthquake is five or six times more powerful than the 5.04 magnitude seismic activity recorded after the North’s fifth nuclear test on Sept. 9, 2016,” said Lee Mi-sun, head of the state weather agency’s earthquake and volcano center here.

“An artificial earthquake was detected in all 150 seismic stations across (South Korea),” she said.

Lee added that the blast power is speculated to reach about 50 kilotons, equal to that of 50,000 tons of TNT explosives. The previous test, also conducted at Punggye-ri, was estimated to have yielded 10 kt.

“Noting that the earthquake’s point of origin is similar to last year’s tremor, it is certain that the blast power has grown stronger,” Lee added.

Meanwhile, the parliament’s defense committee chair, Rep. Kim Young-woo, claimed that the yield of the North’s atomic bomb test could be 10 times more powerful from the previous one conducted last year.

“The explosion was more powerful than the nuclear bomb detonated in Japan’s Nagasaki (in 1945). Four or five times more powerful,” Rep. Kim told local media, citing unnamed sources in Seoul.

Kim also claimed the blast power could have been as high as 100 kt, 10 times that of the fifth test on Sept. 9 last year. 

Several fire departments in the South were reported to have received multiple calls from citizens asking whether there had been an earthquake nearby.

The National Fire Agency announced it had received a total of 31 calls indicating signs of seismic activities from Seoul, Gyeonggi Province, Incheon and other areas, as of 3 p.m.

Incheon Fire Department received four civilian reports from nearby areas at around 12:36 p.m. saying that “the ground was shaking.”

The fire department in Gangwon Province, an area that shares a border with North Korea, also said it received similar calls from residents.

By Jung Min-kyung (mkjung@heraldcorp.com)