Japan Meteorological Agency's earthquake and tsunami observations division director Akira Nagai speaks in front of a monitor showing graphs of ground motion waveform data observed in the morning in Japan during a news conference in Tokyo February 12, 2013. Seismic activities detected at around 0300 GMT in North Korea may be the result of a nuclear test, Japan's top government spokesman said on Tuesday. REUTERS/Toru Hanai (JAPAN - Tags: POLITICS MILITARY)