A dreaded¹ major earthquake in Tokyo would set off a crisis of "toilet refugees," with a restroom shortage for nearly 820,000 people, a government study said.

An expert panel of the government's Central Disaster Prevention Council came to the conclusion this week while studying the potential impact of a 7.3-magnitude earthquake in the tremor²-prone metropolis³.

According to the study, some 817,000 people would find themselves without toilets two hours after such a big tremor, which would cut off 46 percent of Tokyo's water supply.

The wait to use a toilet would be four and a half hours in central Chiyoda ward⁴, home to the headquarters of major companies, government buildings and the imperial palace.

"Besides food and water, shortage of toilets is one of the major issues in post-disaster situations," said Itsuki Nakabayashi, head of the study panel.

The group is advising Tokyo residents always to carry pocket-sized tissue papers or plastic bags for emergency toilet use and urged companies to have portable toilets on standby.

The Japanese government has warned an earthquake with a magnitude of around seven could hit the capital in the coming decades.

Japan is hit by 20 percent of the world's powerful earthquakes.

Much of Tokyo was destroyed in the 1923 Great Kanto Earthquake, which left 142,807 people dead or unaccounted for.

日本政府日前发布一份研究报告称，首都东京若发生大地震，将面临厕所紧缺的危机，届时将会出现近82万“厕所难民”。

该报告由日本政府中央灾害预防学会的一个专家小组编撰，他们研究了地震多发的东京市若发生7.3级以上的强地震，可能会出现哪些潜在问题。

这份于本周发布的报告称，大地震发生时，全市46%的水供应将被中断，约81.7万人在震后两个小时将无厕所可用。

东京市中心的千代田区的厕所在四个半小时后才能恢复使用。千代田区是一些大公司的总部、政府办公楼和皇宫所在地。

专家组负责人中林一树说：“除了食品和水供应，厕所短缺是灾后面临的一个大问题。”

研究小组建议东京市民随身携带纸巾或塑料袋以备不时之需，并敦促公司预备一些可移动厕所。

日本政府警告说，未来几十年东京可能会发生7级左右的大地震。

目前全世界20%的强地震发生于日本。

1923年的关东大地震将东京的大部分地区毁于一旦，这次地震的死亡和失踪人数达142807人。