The United States Geological Survey (USGS) on Thursday detected a 2.9 magnitude quake 23km northeast of Sungjibaegam in North Korea, near the country's nuclear testing site. On September 3, Pyongyang announced a successful test of a hydrogen bomb.
Hong Tae-kyung, a earth science boffin at Yonsei University said: "The reason why Pyunggye-ri has become North Korea's nuclear testing field is because this area was considered stable and rarely saw earthquakes in the past".
The quake took place at 16.41 (UTC) at an estimated depth of 5km, and while the USGS said the quake appeared natural, it did not rule out the possibility of a nuclear test.
"The depth is poorly constrained and has been held to 5 km by the seismologist".
A 3.4 magnitude quake last month near the same location sparked fears there could have been another nuclear test.
There are no nearby tectonic plate faultline boundaries to the test site.
These disturbances are more numerous and widespread than seen after any of the North's previous tests, 38 North has said.
The blast was large enough that residents in China, some 125 miles away, felt the ground shake beneath them. "The recent small quakes suggest that the test might have triggered crust deformation".
North Korea has hinted its next test could be above the ground.
North Korea's foreign minister Ri Yong-ho said that Donald Trump had "lit the wick of war" between countries and that the U.S. would be forced to pay with "a hail of fire". Since North Korea began testing its nuclear capabilities, experts have debated whether explosions at Punggye-ri could trigger another volcanic eruption.