A magnitude-7.1 aftershock rattled Japan today - exactly one month after a massive earthquake which spawned a devastating tsunami.
A warning has been issued for a 3ft (1m) tsunami, the same as after another 7.1 aftershock that shook the north-east coast last week. There was no tsunami after that quake.
People at a large electronics store in central Sendai screamed and ran outside, although the shaking made it hard to move around.
Mothers grabbed their children, and windows shook. After a minute or two, people returned to the store.
The tremor briefly forced Tokyo's main international airport to close both of its runways. The epicentre was just inland and about 100 miles north of Tokyo. The operator of the crippled Fukushima Dai-ichi nuclear complex said the latest quake had no impact on the plant.
There were no new reports of damage. Aftershocks have repeatedly rattled the disaster-weary region, but there is little left in the north-east to ruin. Last Thursday's 7.1-magnitude aftershock, which had been the strongest since the day the original quake hit, did sink hundreds of thousands more households into darkness, however. Most of that electricity has been restored.