The massive exercises were the center of Japan's annual marking of the date in 1923 when a massive quake wrecked the Tokyo region, killing more than 140,000 people and setting fires that left much of the capital in smoking ruins.
In Tokyo, officials acted out a scenario based on a 7.3-magnitude quake hitting the capital at 7:10 a.m. The government has estimated such a temblor could kill some 11,000 people and cause 112 trillion yen (US$1.06 trillion; Ђ811 billion) in damage.
"There have been reports of many deaths and injuries, collapsed buildings and fires," Prime Minister Junichiro Koizumi said in a mock announcement. "Large-scale damage is expected over a wide area."
Officials staged drills in Chiba, just east of Tokyo, deploying police, firefighters, the coast guard and the military. A government mission, headed by Koizumi, was to be dispatched to gauge the simulated damage.
About 1 million people were involved in the drills nationwide, officials said.
The fake quake in Tokyo was followed by a mock earthquake warning in Shizuoka prefecture, 50 kilometers (30 miles) west of the capital, with officials telling residents to prepare for a magnitude-8 quake within a few days.
The exercises came as officials are strengthening preparations in case of a dreaded "big one" hitting Tokyo and its surrounding area home to about one-fourth of Japan's population. Tokyo has a 90 percent chance of being hit by a major quake over the next 50 years, officials say, reports the AP.