South Korea’s military on Sunday said that North Korea is believed to have conducted its sixth nuclear test after it detected a strong earthquake, hours after Pyongyang claimed that its leader has inspected a hydrogen bomb meant for a new intercontinental ballistic missile.
South Korea’s weather agency and the Joint Chief of Staff said an artificial 5.6 magnitude quake occurred at 12:29 p.m. local time, in Kilju, northern Hamgyong Province. The US Geological Survey called the first quake an explosion with a magnitude 6.3.
Shortly after, Yonhap news agency said a second quake was detected with a magnitude 4.6 but South Korea’s weather agency denied another quake occurred. There was no word from the military in Seoul about the possible second quake.
North Korea conducted its fifth test last year in September. If confirmed, the latest test would mark yet another big step forward in North Korean attempts to obtain a nuclear-armed missile capable of reaching deep into the US mainland.
The US State Department had no immediate reaction. South Korea’s presidential office said it will hold a National Security Council meeting chaired by President Moon Jae-in.
North Korea conducted two nuclear tests last year and has since maintained a torrid pace in weapons tests, including flight-testing developmental intercontinental ballistic missiles and flying a powerful midrange missile over Japan.
Earlier on Sunday, photos released by the North Korean government showed Mr. Kim talking with his lieutenants as he observed a silver, peanut-shaped device that was apparently the purported thermonuclear weapon destined for an ICBM.
What appeared to be the nose cone of a missile could also be seen near the alleged bomb in one picture, which could not be independently verified and which was taken without outside journalists present. Another photo showed a diagram on the wall behind Kim of a bomb mounted inside a cone.
As part of the North’s weapons work, Mr. Kim was said by his propaganda mavens to have made a visit to the Nuclear Weapons Institute and inspected a “homemade” H-bomb with “super explosive power” that “is adjustable from tens (of) kiloton to hundreds (of) kiloton.”
North Korea in July conducted its first ever ICBM tests, part of a stunning jump in progress for the country’s nuclear and missile program since Kim rose to power following his father’s death in late 2011.
The North followed its two tests of Hwasong-14 ICBMs, which, when perfected, could target large parts of the United States, by threatening to launch a salvo of its Hwasong-12 intermediate range missiles toward the US Pacific island territory of Guam in August.
It flew a Hwasong-12 over northern Japan last week, the first such overflight by a missile capable of carrying nukes, in a launch Kim described as a “meaningful prelude” to containing Guam, the home of major US military facilities, and more ballistic missile tests targeting the Pacific.
Vipin Narang, an MIT professor specializing in nuclear strategy, said it’s important to note that North Korea was only showing a mockup of a two-stage thermonuclear device, or H-bomb. “We won’t know what they have until they test it, and even then there may be a great deal of uncertainty depending on the yield and seismic signature and any isotopes we can detect after a test,” he said.
To back up its claims to nuclear mastery, such tests are vital. The first of its two atomic tests last year involved what Pyongyang claimed was a sophisticated hydrogen bomb; the second it said was its most powerful atomic detonation ever.
It is almost impossible to independently confirm North Korean statements about its highly secret weapons programme.
South Korean government officials said the estimated explosive yield of last year’s first test was much smaller than what even a failed hydrogen bomb detonation would produce. There was speculation that North Korea might have detonated a boosted fission bomb, a weapon considered halfway between an atomic bomb and an H-bomb.
North Korea is thought to have a growing arsenal of nuclear bombs and has spent decades trying to perfect a multistage, long-range missile to eventually carry smaller versions of those bombs.
The North said in its statement that its H-bomb “is a multi-functional thermonuclear nuke with great destructive power which can be detonated even at high altitudes for super-powerful EMP (electromagnetic pulse) attack according to strategic goals.”
Kim, according to the statement carried by the state-run Korean Central News Agency, claimed that “all components of the H-bomb were homemade ... thus enabling the country to produce powerful nuclear weapons as many as it wants.”
