The Chinese administration said in a statement on its website that the quake was recorded at a depth of zero kilometers, while Xinhua said the epicenter was in roughly the same place as a similar shallow earthquake on 3 September, which turned out to be caused by North Korea's sixth and largest nuclear test.
However, in analyzing the same earthquake, South Korea came to a different conclusion, and said it was likely to be natural or man-made such as a nuclear test. South Korea's weather agency assessed the seismic activity as a natural event.
"The quake is presumed to have occurred naturally," an agency official said, according to South Korea's Yonhap news agency. "A sound wave, which is usually generated in the event of an artificial earthquake, was not detected."
"We use several methods to tell whether earthquakes are natural or manmade," an official, who asked for anonymity, told the Independent. "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 manmade earthquake. In this case we saw none. So as of now we are categorizing this as a natural earthquake."