A Japanese panel Tuesday warned of the high likelihood of a massive earthquake off the shore of its northernmost main island, Hokkaido, in the Chishima trench over the next 30 years. Officials warned that the next quake could be on the scale of the magnitude of the Great East Japan Earthquake that devastated the country in 2011.

The Headquarters for Earthquake Research Promotion outlined the first revision on earthquake predictions in 30 years. Experts warned that there was between a 7 and 40 percent chance of a magnitude 8.8 or greater earthquake striking in the ocean just south of Hokkaido. They said there was a 70 percent chance of an earthquake between magnitudes 7.8 and 8.5 striking offshore from the city of Nemuro and a 60 percent chance of a similar scale earthquake striking the smaller islands north of Hokkaido.

Earthquakes are measured on the Richter magnitude scale, a logarithmic assessment of the natural disaster’s strength. Magnitude 7 is considered “great” and will damage most buildings. Magnitude 9 and above causes an extremely high level of destruction. The higher the magnitude of the earthquake, the rarer it is. The most powerful earthquake ever recorded was the 1960 Valdivia Earthquake in Chile, which was a 9.5 on the Richter scale.

The 2011 Great East Japan Earthquake was the most powerful ever recorded in Japan, and the fourth most powerful in the world since scientists began recording them in 1900. The 2011 earthquake and ensuing tsunami resulted in a meltdown at the Fukushima Daiichi Nuclear Power Plant. The natural disasters killed nearly 16,000 and the World Bank estimated the total cost of the earthquake and tsunami was roughly $235 billion.

The panel said that earthquakes of this magnitude had struck the area near Hokkaido approximately once every 340 to 380 years and believe the last major quake to have occurred 400 years ago.

“I hope disaster preparations are reviewed based on the possibility that a super-gigantic quake like the one that struck the Tohoku region could also strike Hokkaido,” said Naoshi Hirata, a seismology professor who chair’s the government panel’s Earthquake Research Committee.

The Japanese Central Disaster Management Council estimated in 2006 that around 900 people could be killed by an earthquake of this size and the tsunami it would produce.

Hokkaido is less densely populated than Japan’s main island, Honshu, home to the country’s capital, Tokyo, but officials said tsunamis from an earthquake in the Chishima trench could affect both islands.