Experts have been quick to deny that a magnitude 6.0 earthquake off the coast of North Korea was caused by a nuclear bomb.
The hermit nation was rocked by the earthquake that is believed to have been a natural occurrence, nearly 350 miles below the seabed.
It is unlikely to have caused any damage on the surface, but early speculation suggested that it had been Kim Jong un testing an atomic weapon.
On July 4, Pyongyang test-launched its first intercontinental ballistic missile. North Korea’s five previous nuclear tests caused signs of artificial quakes.
Analysts say North Korea needs to conduct another atomic test explosion to perfect a nuclear-tipped missile capable of reaching the continental U.S.
The quake was centred far offshore and very deep while North Korea’s past nuclear tests were conducted on land.
According to the US Geological Survey, the quake struck 116 miles southeast of the northern port city of Chongjin. The epicenter was 347 miles below the seabed.
Cho Ik-hyun at South Korea’s state weather agency said the depth shows it was a natural event, too deep for a possible nuclear blast.
Natural earthquakes create different seismic patterns from ones caused by humans. South Korea’s Defense Ministry said there was no indication that North Korea had carried out a nuclear test.
Cho said any earthquake deeper than 43 miles normally causes little damage on the surface.
Even if a ship was sailing over the epicentre at the time of the quake, it wouldn’t have noticed anything, Cho said.
Earthquakes are rare on the Korean Peninsula, unlike in neighbouring Japan. Two quakes measuring 5.1 and 5.8 jolted southeastern South Korea on September 12, causing no casualties.