AP via USA Today, February 12, 2013
SEOUL, South Korea (AP) -- South Korea said it suspects a nuclear test caused an earthquake Tuesday in North Korea just north of a site where the country conducted two previous atomic tests. North Korea has yet to confirm whether the tremor resulted from a widely anticipated third nuclear test, though an analyst in Seoul said a nuclear detonation was a "high possibility."
[...]
"There is a high possibility that North Korea has conducted a nuclear test," said Chi Heoncheol, an earthquake specialist at the institute. Chi said a magnitude 3.9 magnitude earthquake and a magnitude 4.5 earthquake were detected in the North's 2006 and 2009 nuclear tests.
(Full Story)
Apparently the detected "quake" for this one was 5.1 so I guess it was a larger test, and SK has also confirmed that a test was conducted. No news from NK yet.