A Fourth Nuclear Test From North Korea?

North Korea successfully tested a miniaturized hydrogen nuclear device, Jan. 6, according to state media. If true, this is the first such device fielded by Pyongyang. South Korea initially picked-up seismic activity centered near North Korea's suspected nuclear test site. Initial estimates gave readings measuring between 4.2 and 5.1 magnitude, raising the suspicion that the tremor was caused by a nuclear test, as opposed to a natural earthquake. A nuclear bomb test in the same area in 2013 triggered a 5.1-magnitude quake. North Korean media soon followed up with an official announcement, confirming the successful test....