A strong earthquake struck Japan's northeast Monday on the one-month anniversary of the massive quake and tsunami wave that devastated Japan's northeastern coast and unleashed the worst nuclear crisis since Chernobyl.
The 6.6-magnitude aftershock briefly forced Tokyo's main international airport to shut down its runways.
Workers at the crippled Fukushima Daiichi nuclear plant were asked to evacuate.
According to the USGS, the epicentre was 163 kilometres NNE of Tokyo in the Eastern Honshu region. It occurred at a depth of 10 kilometres.
A warning was issued for a one metre tsunami, but has since been lifted. The same warning was put into effect last week when an aftershock hit the northeast coast. That quake did not generate a tsunami.
According to reports, people at a large electronics store in the northeastern city of Sendai screamed and ran outside -- but the shaking was so intense, it was difficult to move.
There have been no new reports of damages.
The 9.0-magnitude quake that triggered the tsunami on March 11 are believed to have killed more than 25,000 people and caused as much as $310 billion in damage.
The nuclear plant has been leaking radiation ever since, and officials don't know how long it will take to cool the reactors.
With files from The Associated Press and CNN