A powerful earthquake with a magnitude of 7.2 rocked rural northern Japan on Saturday, killing at least six people, injuring more than 200 and sending landslides sweeping down mountainous hillsides.

Following are some facts about Japan and earthquakes.

* Japan, situated on the "Ring of Fire" arc of volcanoes and oceanic trenches which partly encircles the Pacific Basin, accounts for about 20 percent of the world's earthquakes of magnitude 6 or greater.

* A tremor occurs in Japan at least every five minutes, and each year there are up to 2,000 quakes that can be felt by people.

* The Great Kanto earthquake of September 1, 1923, which had a magnitude of 7.9, killed more than 140,000 people in the Tokyo area. Seismologists have said another such quake could strike the city at any time.

* On January 16, 1995, an earthquake with a magnitude of 7.3 hit central Japan, devastating the western port city of Kobe. It was the worst earthquake to hit Japan in 50 years, killing more than 6,400 and causing an estimated $100 billion in damage.

* On October 23, 2004, a 6.8 magnitude quake struck the Niigata region, about 250 km (150 miles) north of Tokyo, killing 65 people and injuring 3,000.

* On March 25, 2007, a 6.9 magnitude quake struck the Noto peninsula in Ishikawa prefecture, about 300 km west of Tokyo, killing one person, injuring more than 200 and destroying hundreds of homes.

* On July 16, 2007, a 6.8 magnitude quake struck Niigata prefecture, about 250 km (150 miles) northwest of Tokyo, killing 11 people and injuring 1,950. The tremor caused radiation leaks at the world's largest nuclear plant, which officials said were within safety regulations and posed no threat to the environment. The leaks nonetheless reignited fears about nuclear safety in the quake-prone country.

* The Tokyo metropolitan government said in March 2006 that a magnitude 7.3 earthquake under Tokyo would probably kill more than 5,600 people and injure almost 160,000. Official estimates of economic damage have topped more than $1 trillion.

* In a report published in 2004, German insurer Munich Re was even more pessimistic, saying a severe earthquake in the Tokyo-Yokohama area would kill hundreds of thousands of people, cause damage running into trillions of dollars and have global economic repercussions.

* The Tokyo-Yokohama metropolis, with a population of 35 million, has the highest "at risk" rating from natural disasters such as earthquakes of any of the world's 30 "megacities", the report said.