WASHINGTON _ U.S. and international intelligence analysts will pore over all aspects of North Korea's Sunday weapon test, including sampling air for radioactive particles and studying seismic shock waves, to determine if it did detonate a hydrogen bomb.
The analysis, which is likely to take weeks, seeks to confirm the size of the detonation, the weapon design and the radioactive fuel used.
Discovering the size of the weapon takes on increased importance since North Korea successfully launched two intercontinental ballistic missiles _ weapons in theory capable of striking the U.S. mainland _ in July.
Although North Korea has developed and tested nuclear weapons before, it is not clear that the nation has developed a nuclear warhead small enough to fit atop a long-range missile or robust enough to survive the missile's fiery re-entry into the atmosphere.
But the series of underground nuclear tests and increasingly sophisticated missile flights have led to concerns that North Korea can now strike the U.S. mainland.
An analysis by the U.S. Geological Survey fixed the coordinates of the detonation in the northeast sector of North Korea, an isolated and heavily forested area about 6,000 feet in elevation. The nearest city or town is 14 miles away.
The blast registered on seismographs at about 6.3 in magnitude, which is more powerful than the 5.1 registered in North Korea's last test in September and earlier in 2013.
The Comprehensive Nuclear-Test-Ban Treaty Organization, a multinational group that monitors nuclear testing worldwide, said more than 100 of its land-based monitoring stations detected the explosion, and the early analysis confirmed the event was larger than last year's nuclear test.
"It constitutes yet another breach of the universally accepted norm against nuclear testing; a norm that has been respected by all countries but one since 1996," Lassina Zerbo, head of the Vienna-based organization, said Sunday in a statement.
"It also underlines yet again the urgent need for the international community to act on putting in place a legally binding ban on nuclear testing once and for all."
The Air Force Technical Applications Center at Patrick Air Force Base, Fla., is responsible for analyzing captured data for the U.S. military. Analysts with the center pore over seismology and launch a so-called nuclear sniffer plane, WC-135 Constant Phoenix, to detect radioactivity.
North Korea has fired 21 missiles during 14 tests since February, including one last Monday that flew over northern Japan. If confirmed, the weekend test would be the sixth nuclear test.
North Korean leader Kim Jong Un has repeatedly threatened the U.S. territory of Guam, which is home to U.S. Navy and Air Force bases and thousands of troops.
