Japan issues megaquake advisory after magnitude 7.5 tremor

Officials said the advisory was not a prediction and the probability of a magnitude 8 or larger quake is only about 1 per cent. But there’s hope the advisory will serve as a wake-up call for a quake that could have the devastation of the 2011 disaster that killed nearly 20,000 people and destroyed a nuclear plant.

There is an increased risk of a magnitude 8 or larger earthquake in the coming week. Officials are urging residents, especially along coastal areas, to be well prepared so they can grab an emergency bag and run as soon as possible if a bigger quake hits.

The Japan Meteorological Agency (JMA) said that Monday’s powerful quake temporarily increased potential risks in the regions of Hokkaido and the Sanriku coast. That’s where the Pacific Plate beneath Japan forms the two trenches – the Japan Trench and Chishima Trench – that have caused many large quakes in the past.

Experts said the deadly quake and tsunami in 2011 was caused by movement associated with the Japan Trench. It spans from off the eastern coast of Chiba to Aomori, and the Chishima Trench goes from the eastern coast of Hokkaido to the northern islands and the Kurils.