A tsunami alert has been issued for Japan's northeast coast after a strong earthquake shook buildings as far away as Tokyo. The tremor struck in the Pacific Ocean at a depth of 23 miles, and the epicentre was 285 miles from the capital. The earthquake had a preliminary magnitude of 7.3, the US Geological Survey said, adding that there was no risk of a widespread tsunami. An alert for a one-metre high tsunami was issued for the coast of Miyagi Prefecture in northeastern Japan, which was hit by a devastating earthquake and tsunami on March 11, 2011. That quake triggered fuel-rod meltdowns at the Fukushima nuclear plant, causing radiation leakage, contamination of food and water and mass evacuations in the world's worst nuclear crisis since Chernobyl in 1986. Tokyo Electric Power Co, the operator of the Fukushima nuclear plant, reported no irregularities at its nuclear plants after the latest quake.