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BREAKING: Nuclear Test in North Korea?

4.9 earthquakes (or many earthquakes) probably do not occur very often on North Korean soil. Just nuclear warhead tests. The reason I say this is I have an iPhone app for earthquakes on my phone and there have been very few if any on NK soil in past 2 years.

If certain suspicions are confirmed, this is a major development:
 

The U.S. Geological Survey said Tuesday it had detected a magnitude 4.9 earthquake in North Korea, but neither Pyongyang nor Seoul confirmed whether North Korea had conducted its widely anticipated third nuclear test. The South Korean Defense Ministry said it was trying to determine whether North Korea had conducted a nuclear test. Nuclear blasts can create tremors but they are distinct from those caused by natural earthquakes. North Korea's powerful politburo vowed to continue firing "powerful long-range rockets," but a statement Tuesday made no mention...