Japan lifts megaquake advisory week after powerful tremor

The December 8 quake triggered tsunami waves of up to 70 centimetres (28 inches) and injured more than 40 people, but no major damage was reported, according to the Japan Meteorological Agency (JMA) and the Fire and Disaster Management Agency (FDMA).

In the wake of the tremor, JMA officials issued a rare advisory, warning of an elevated risk of a megaquake -- defined as magnitude 8.0 or larger tremor -- in the north of the country.

Scientists say that after an earthquake of magnitude 7.0 or larger, there is a one percent chance of a megaquake within seven days, and the advisory urges people to prepare emergency bags should they need to evacuate quickly.

According to the government's disaster prevention guidelines issued in March, an offshore megaquake in the Hokkaido-Sanriku region -- where the latest advisory applied -- could cause a tsunami up to 30 metres and kill as many as 199,000 people.

It could also destroy up to 220,000 houses and buildings and cause up to 31 trillion yen ($200 billion) in economic damage, the guidelines said.