People watch a television broadcast reporting the North Korea's nuclear test at the Seoul Railway station on February 12, 2013 in Seoul, South Korea.
Fear, concern after North Korea nuclear test —
People watch a television broadcast reporting the North Korea's nuclear test at the Seoul Railway station on February 12, 2013 in Seoul, South Korea.
Chung Sung-Jun/Getty Images
A North Korean soldier rides a bike beside a river crossing on the Yalu River near the North Korean town of Sinuiju on February 12, 2013.
A North Korean soldier rides a bike beside a river crossing on the Yalu River near the North Korean town of Sinuiju on February 12, 2013.
MARK RALSTON/AFP/Getty Images
South Korean conservative protesters position a defaced North Korean flag as they participate in a rally demonstrating against North Korea's nuclear test on February 12, 2013 in Seoul, South Korea.
Fear, concern after North Korea nuclear test —
South Korean conservative protesters position a defaced North Korean flag as they participate in a rally demonstrating against North Korea's nuclear test on February 12, 2013 in Seoul, South Korea.
Chung Sung-Jun/Getty Images
Japanese Prime Minister Shinzo Abe leaves his official residence after he attended the security council meeting in Tokyo on February 12, 2013.
Fear, concern after North Korea nuclear test —
Japanese Prime Minister Shinzo Abe leaves his official residence after he attended the security council meeting in Tokyo on February 12, 2013.
YOSHIKAZU TSUNO/AFP/Getty Images
An official of the Korea Meteorological Administration shows a seismic image of a tremor caused by North Korea's nuclear test.
Fear, concern after North Korea nuclear test —
An official of the Korea Meteorological Administration shows a seismic image of a tremor caused by North Korea's nuclear test.
KIM JAE-HWAN/AFP/Getty Images
A North Korean soldier patrols along the Yalu River near the North Korean town of Sinuiju on February 12, 2013.
Fear, concern after North Korea nuclear test —
A North Korean soldier patrols along the Yalu River near the North Korean town of Sinuiju on February 12, 2013.
MARK RALSTON/AFP/Getty Images
North Korea said Tuesday that it had conducted a new, more powerful underground nuclear test using more sophisticated technology.
Fear, concern after North Korea nuclear test —
North Korea said Tuesday that it had conducted a new, more powerful underground nuclear test using more sophisticated technology.