Quake center records N. Korea event
If you live on the West Coast of the United States, there's a decent chance that you've visited the U.S. Geological Survey's Web site at some point to check information about an earthquake in your area. But since last night, traffic has spiked for reasons other than a natural temblor.
North Korea's claim of a nuclear weapons test has sent people to the USGS site to look for seismic evidence on their own. This page shows a 4.2-magnitude event about 240 miles northeast of Pyongyang at the appointed hour.