The area where the quake struck, authorities said was near the nation's known nuclear test site. She says it was clear that the quake wasn't caused by an artificial explosion.
If it is confirmed as a nuclear test, it would be the North Korean regime's seventh.
"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 natural disaster", said the official, who asked for anonymity.
Earlier this month, when North Korea conducted its sixth and most powerful nuclear test ever, officials detected a 6.3-magnitude natural disaster, which was followed by a 4.1-magnitude quake - caused by the collapse of a tunnel at the mountainous site.
Two South Korean officials at the Korea Meteorological Administration told CNN that their analysis so far suggests Saturday's seismic activity around the nuclear site was not caused by an explosion or a collapse of the site. The activity took place around 50 km (31 miles) from previous nuclear tests, it added. "So as of now, we are categorising this as a natural quake". The depth of the quake was 5 kilometers (3.1 miles).
China will suspend such exports once the total exports approaches the ceiling.
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The president's bellicose rhetoric was in turn answered by Kim in a rare personal statement broadcast on state television. President Donald Trump delivered a stern warning to North Korea over its ballistic missile launches and nuclear tests.
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During the Friday remarks, Trump , who at times seemed to take on a Southern accent, also expressed his displeasure with Sen. Tillerson won't say what the US response would be if Kim's government tested a hydrogen bomb in the Pacific Ocean .
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Carroll remains a huge threat in the air, but he might find himself pushed towards the halfway line too frequently. David Howells must have thought he'd earned Spurs a point before Julian Dicks' penalty won it for the Hammers .
Ri is due to address the United Nations later on Saturday.
Saturday's detection comes at a time of rising tensions between the United States and North Korea, with North Korean dictator Kim Jong Un and President Donald Trump engaging in an escalating war of words.
Beijing is also banning imports of textiles, one of Pyongyang's last major sources of foreign revenue.
Yonhap reports, however, that as of right now, "it is presumed to be a natural quake".
China will restrict oil exports to and ban textile imports from North Korea, the commerce ministry announced today, as Beijing joined global efforts to enforce tighter UN Security Council sanctions on Pyongyang for its provocative nuclear and missile tests.