A small artificial earthquake has been recorded in North Korea, around 34km (21 miles) southeast of the capital of Pyongyang. The 2.2 magnitude earthquake is thought to have been caused by a blasting work – not nuclear tests – South Korea's meteorological agency said.
According to the Yonhap News Agency, the earthquake took place around 12.30pm local time. Korea Meteorological Administration (KMA) said the earthquake struck at a depth of 1km, suggesting it was caused by a blast. "The quake is not believed to be the result of a nuclear test, considering its location or magnitude," a KMA source said.
In January, North Korea was hit by a 4.8 magnitude earthquake (with some reporting 5.1), near the Punggye-ri nuclear test site in the country's north-east. Japan's meteorological agency said it was unlikely the earthquake was natural. Instead, it said it could have resulted from nuclear tests.
At the time, North Korea said it had detonated a hydrogen bomb – although this claim was later disputed by scientists and world leaders. Experts from the Lamont-Doherty Earth Observatory said the seismic pattern it produced was very similar to those seen from nuclear tests, so could not have been the result of a hydrogen bomb.
Regardless, there are a number of concerns about the effects North Korea's nuclear testing will have. In February, a study published in the journal Nature said nuclear tests could cause the country's biggest volcano, Mount Paekdu, to erupt.
The research found strong ground motions from explosions could disturb the magma chamber of the volcano. "An underground nuclear explosion test near an active volcano constitutes a direct threat to the volcano. This study examined the dynamic stress changes of the magma chamber of Baekdusan [Changbaishan] that can be induced by hypothetical North Korean nuclear explosions."