BEIJING/HONG, KONG/SHANGHAI/SEOUL – China’s earthquake administration said on Saturday it had detected a magnitude 3.4 earthquake in North Korea that was a “suspected explosion,” raising fears the isolated state had conducted another nuclear bomb test weeks after its last one.
An official at South Korea’s meteorological agency said it was analyzing the tremor, which they put at magnitude 3.0, but the initial view was that it was a natural quake.
“We use several methods to tell whether earthquakes are natural or man-made,” said the official, who asked for anonymity in light of office rules. “A key method is to look at the seismic waves or seismic acoustic waves and the latter can be detected in the case of a man-made earthquake. In this case we saw none. So as of now we are categorizing this as a natural earthquake.”
The earthquake was detected in Kilju county in North Hamgyong Province, where North Korea’s known Punggyeri nuclear site is located, the official said.
The Chinese administration said in a statement on its website that the quake, which occurred around 4:29 p.m. local time, had a recorded depth of zero km.
All of North Korea’s previous six nuclear tests registered as earthquakes of magnitude 4.3 or above. The last test, on Sept. 3, registered as a 6.3 magnitude quake. The test escalated tensions with the U.S. and its neighbors, and this week the regime’s foreign minister said the country’s options included testing a hydrogen bomb in the Pacific Ocean.
There have been concerns about the stability of the nuclear test site since the Sept. 3 test. Website 38 North said satellite imagery taken after that test appeared to show landslides atop the site that were more numerous and widespread than after the previous five tests.
The site, run by the U.S.-Korea Institute at Johns Hopkins University’s School of Advanced International Studies, added the bomb’s 250-kiloton yield was close to what it previously determined was the maximum that could be contained by the test site.
The early September detonation followed two intercontinental ballistic missile launches in July that brought Kim Jong Un’s isolated regime a step closer to achieving its aim of being able to strike the continental U.S. with a nuclear warhead.
On Thursday, North Korea struck back at U.S. President Donald Trump’s threats to destroy it, with Kim warning of the “highest level of hardline countermeasure in history” and his foreign minister suggesting that could include testing a hydrogen bomb in the Pacific Ocean.
The foreign minister, Ri Yong Ho, who was speaking to reporters in New York, where he is attending the United Nations General Assembly, said in remarks broadcast on South Korean TV that the countermeasures might refer to a “strongest-ever” ground-level test of a hydrogen bomb in the Pacific.
His comments came after Trump ordered new sanctions on individuals, companies and banks doing business with North Korea as he sought to further isolate the regime and increase economic pressure to curb its weapons programs.
Earlier this month, Pyongyang fired its second missile in as many months over northern Japan into the Pacific Ocean. Since Kim came to power after the death of his father Kim Jong Il in 2011, he has ramped up nuclear and missile weapon tests.
U.S. analysts now estimate that North Korea may have as many as 60 nuclear weapons, according to a Washington Post report. That’s in addition to cyberwarfare capabilities, a biological weapons research program and a chemical weapons stockpile. It also has a vast array of conventional artillery aimed at Seoul.