A 2.7 magnitude quake was detected Friday near a nuclear test site in North Korea, which the Korean weather authorities assessed to be natural. But South Korea's Meteorological Administration says the quake was natural.
Experts say the small quakes that occurred after the test may have been linked to the nuclear detonation, with some suggesting a possible increase of geological stress in the area.
The US Geological Survey assessed it to be of 2.9 magnitude, originating 23 kilometers northeast of Sungjibaegam, Ryanggang Province, in North Korea.
It was centred very close to North Korea's Punggye-ri Nuclear Test Site, which previous weapons tests have been detected at through the earthquakes they generate.
The series of quakes has prompted experts and observers to suspect the last test - which the North claimed to be of a hydrogen bomb - may have damaged the mountainous location in the northwest tip of the country, where all of North Korea's six nuclear tests were conducted.
Seismic activity does not always indicate a nuclear test. "If it goes ahead with another test in this area, it could risk radioactive pollution".
The magnitude of the test was much lower than the North's most recent nuclear test on September 2, which measured 6.3 on the Richter scale.
These disturbances are more numerous and widespread than seen after any of the North's previous tests, 38 North has said.
The China Earthquake Networks Center (CENC) said the event may have been caused by an artificial explosion, but the Executive Secretary of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) Lassina Zerbo said the quake was unlikely to be manmade. On September 3, Pyongyang announced a successful test of a hydrogen bomb. In 2006, North Korea's first detonation triggered a 4.1-magnitude quake.