Prime Minister Shinzo Abe, wearing light-blue work gear, declared a mock state of emergency at his office, where defense, police and fire officials gathered for the simulated drills.
More than 600,000 people across Japan participated, commemorating the Sept. 1, 1923 Great Kanto earthquake, a magnitude-8.3 temblor in Tokyo that killed more than 140,000 people.
Saturday's drills came weeks after a magnitude-6.8 quake in central Niigata prefecture (state) killed 11 people and injured more than 1,000. The July 16 temblor also caused malfunctions and leaks at the Kashiwazaki-Kariwa nuclear power plant, raising concerns about safety at Japan's nuclear power stations.
"The foundation of nuclear power policy is the public trust and safety. We must take all possible steps to ensure safety procedures at nuclear power plants,'' Abe was quoted by Kyodo News agency as telling reporters after observing drills later Saturday at Izu City in Shizuoka.
In Shizuoka _ about 150 kilometers (95 miles) west of Tokyo _ where experts say a major quake is due any time, prefectural and utility officials inspected Hamaoka Nuclear Power Plant, simulating information relays and firefighting procedures. Citizens practiced carrying the injured on stretchers.
The U.S. Navy in Japan also participated for the second straight year. The USS Tortuga and its crew were sent from the Yokosuka naval base near Tokyo to evacuate Japanese commuters from quake-affected areas. A UH-60 Black Hawk helicopter from nearby Camp Zama transported medical and other relief supplies.
Japan is one of the world's most earthquake-prone nations, and Tokyo has a 90 percent chance of being hit by a major quake over the next 50 years, officials say.
The government has estimated that 11,000 people would die and Japan would suffer about 112 trillion yen (US$950 billion; euro790 billion) in economic damages if a major earthquake were to strike Tokyo, home to about 35 million residents, or one-fourth of the country's population.