japan earthquake
USGS
UPDATE: All tsunami warnings have since been lifted.
3:38 AM: At 3:18 AM EST this morning, an earthquake of 7.3 magnitude struck off the northeast coast of Japan. This is according to the USGS.  Earlier, the USGS reported it as a 7.4 magnitude earthquake.
A 1 meter high tsunami warning had been issued for the Miyagi prefecture, according to Japan's NHK.
CNBC reported that buildings were shaking in Tokyo. 
Currently, there are no reports of major damage.
"Tokyo Electric says no irregularities seen in radiation levels at Fukushima Daiichi nuclear plant after Japan quake," reports Reuters.