Seismic activity in North Korea seems to indicate truth to report of nuclear test

A U.S. military official told CNN that "something clearly has happened," but the Pentagon was working to fully confirm the report.
Other senior U.S. officials said they also believed the test took place, citing seismic data that appears to show one.
The U.S. Geological Survey Web site recorded a light 4.2-magnitude earthquake in North Korea at 10:35 a.m., about 385 kilometers (240 miles) northeast of the North Korean capital, Pyongyang.
South Korean intelligence officials said a seismic wave of magnitude-3.58 had been detected in North Hamkyung province.