Big Tokyo quake to cram streets in rush for home

TOKYO, April 3 (Reuters) - A big earthquake in Tokyo during the day would force more than 12 million people to try to walk home, cramming streets and causing confusion, the government said.

Tokyo's transport network would stop running, leaving people with journeys of up to 15 hours on foot to get home on roads packed with people -- possibly more than six people per square metre (11 square feet), similar to a rush-hour train, it said.

Earthquakes are common in Japan, one of the world's most seismically active areas, with up to 140,000 people killed in the last big quake in Tokyo in 1923, many of them in the resulting fires.

"We want to discourage people from rushing home by making sure they have the means to check the safety of their family," Natsuo Ito, deputy director of earthquake and volcanic disaster management at the Cabinet Office, said on Thursday.

"It's also important to encourage schools and companies to stock up on food and water so people can stay put for some time," he said, adding that the government would compile measures by the end of March next year.

The Tokyo metropolitan government said in 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.

The greater Tokyo region, with a population of 12 million, sits on the junction of four tectonic plates: the Eurasian, North American, Philippine and Pacific. The sudden bending or breaking of any plate can trigger an earthquake. (Reporting by Chisa Fujioka; Editing by Rodney Joyce)