This article is more than 2 years old

This article is more than 2 years old

A series of earthquakes in North Korea have sparked fears the country may have conducted another nuclear weapons test, although experts said the tremors were natural.

Speculation around further testing came as US air force bombers flew east of North Korea on Saturday in ‘demonstration of US resolve’, said Pentagon officials.

China was first to announce the seismic events and said the larger 3.4 magnitude quake was a “suspected explosion”.

However, an official at South Korea’s meteorological agency said its initial analysis of the tremor, which it put at magnitude 3.0, showed it was a natural quake and other experts doubted the temblors were related to a weapons test.

The intense scrutiny of any earthquakes in North Korea highlight rising tensions in the region as Donald Trump and Kim Jong-un engage in an escalating war of words.

North Korea’s foreign minister suggested a nuclear test over the Pacific Ocean would be an appropriate response to Trump’s recent comments and some analysts believed Kim might test missiles or nuclear weapons in response.

“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,” said the unnamed South Korean official. “In this case we saw none. So as of now, we are categorising this as a natural earthquake.”

The earthquake was detected in Kilju county in North Hamgyong province, where the Punggye-ri nuclear site is located, the official said. The tremor was smaller than any other associated with North Korea’s nuclear weapons programme.

Play Video 2:26 Trump: I’ll handle ‘little rocket man’ Kim Jong-un – video

A second, much smaller earthquake was detected earlier, according to the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO), a group tasked with monitoring weapons tests.

Both quakes were “unlikely man-made” and occurred 31 miles (50km) from the site of previous tests, according to Lassina Zerbo, head of the CTBTO, who said they were similar to tremors recorded after North Korea’s recent and most powerful nuclear test.

China’s earthquake administration said in a statement on its website that the quake, which occurred around 0830 GMT, was recorded at a depth of zero miles. The US Geological Survey said the quake was at a depth of three miles.

“This event occurred in the area of the previous North Korean nuclear tests,” the USGS said. “We cannot conclusively confirm at this time the nature (natural or human made) of the event.”

Meanwhile, US air force B-1B Lancer bombers escorted by fighter jets flew in international airspace over waters east of North Korea on Saturday, in a show of force the Pentagon said demonstrated the range of military options available to Trump.

The flight, which was disclosed shortly before North Korea’s foreign minister was due to address the United Nations, was the farthest north of the demilitarised zone separating North and South Korea that any US fighter jet or bomber has flown in the 21st century, the Pentagon said.

“This mission is a demonstration of US resolve and a clear message that the President has many military options to defeat any threat,” said Pentagon spokeswoman Dana White.

All of North Korea’s previous six nuclear tests registered as earthquakes of magnitude 4.3 or above. The last test on 3 September registered as a 6.3 magnitude quake. A secondary tremor detected after that test could have been caused by the collapse of a tunnel at the mountainous site, experts said at the time.

Q&A What threat does North Korea pose to South Korea? Show Hide The North may have found a way to make a nuclear warhead small enough to put on a missile, but firing one at the South is likely to provoke retaliation in kind, which would end the regime. Pyongyang has enough conventional artillery to do significant damage to Seoul, but the quality of its gunners and munitions is dubious, and the same problem – retaliation from the South and its allies - remains. In the event of a non-nuclear attack, Seoul's residents would act on years of experience of civil defence drills, and rush to the bomb shelters dotted around the city, increasing their chances of survival.

Satellite photos of the area after the 3 September quake showed numerous landslides, apparently caused by the blast, which North Korea said was an advanced hydrogen bomb.

Russia’s emergency ministry said background radiation in nearby Vladivostok was within the natural range.

There was no immediate reaction from China’s foreign ministry, but the news was widely reported by Chinese state media outlets and on social media.



Tensions have continued to rise around the Korean peninsula since Pyongyang carried out its sixth nuclear test, prompting a new round of UN sanctions.

North Korea’s foreign minister, Ri Yong Ho, who is in New York for a UN meeting, warned on Thursday that Kim could consider a hydrogen bomb test of an unprecedented scale over the Pacific. Ri is due to address the UN later on Saturday.

The US president called the North Korean leader a “madman” on Friday, a day after Kim dubbed him a “mentally deranged US dotard” who would face the “highest level of hardline countermeasure in history”.

North Korea has launched dozens of missiles this year, several of them flying over Japan, as it accelerates a weapons programme aimed at enabling it to target the United States with a nuclear-tipped missile.

China has been angered by the tests and has signed up for the increasingly tough UN sanctions, but it has stressed the need to resume dialogue and for all sides to take steps to reduce tensions.

Earlier on Saturday, China said it would limit exports of refined petroleum products from 1 October and ban exports of condensates and liquefied natural gas immediately to comply with the latest UN sanctions. It will also ban imports of textiles from North Korea.