Justin Mccurry in Tokyo

On the 20th floor office in Toyko that Japan's foreign correspondents call home, veterans of previous big earthquakes exchanged worried glances. Only one - an Italian - did what we were supposed to do and huddled beneath his desk.

The block swayed to the accompaniment of the sinister sound of creaking concrete, a sound which is never forgotten. One hundred and fifty miles away in Niigata prefecture, 30 died and tens of thousands were left homeless, but Tokyo escaped unscathed that night. It might not be so fortunate next time.

The capital lies in one of the most quake-prone areas of a country that accounts for a fifth of the world's powerful earthquakes, those of magnitude 6 or above on the Richter scale. In 1923, the last time a major earthquake hit Tokyo, more than 140,000 died as neighbourhoods of wooden houses collapsed or burned to the ground.

Most of today's Tokyo is made of sterner stuff, with modern structures designed to withstand the impact of fairly powerful earthquakes.

There the reassurance ends. There is a 70% chance of an earthquake of Richter magnitude 7 striking Tokyo within the next 30 years.

That is about the same strength as the 1995 quake in Kobe which killed more than 6,000 people. In Tokyo the toll would exceed 7,000 with 160,000 injured. More than 140,000 buildings would be destroyed or badly damaged.

The implications are too awful to contemplate. Just about every political decision is made here, and the local economy accounts for 17% of Japan's GDP.

The Niigata quakes have at least proved that the government is better prepared than it was nine years ago, when whole neighbourhoods of Kobe were left to burn while officials in Tokyo debated the political pros and cons of sending in the armed forces.

Offers of help from abroad were turned down, even as people were being pulled out of the rubble. The homeless turned to the city's well-organised mafia for emergency food, water and clothing. By contrast, Japanese troops were quickly on the scene in Niigata, airlifting stranded villagers and distributing relief supplies.

But hospitals in the mainly rural region were unprepared for the deluge of injured. Tens of thousands of people still face shortages of food, medicine and clothing, evacuation centres lack heat, and there is a shortage of temporary toilets.

Fewer than half of Japan's 130,000 schools - which are turned into evacuation centres - are capable of withstanding a big earthquake, and 14m ageing wooden homes need reinforcement.

In Tokyo, where more than 1.6m homes were built before 1981, residents of traditional wooden homes would form the bulk of the casualties in a major quake, according to experts. Subsidies exist to bolster such structures, but they cover a fraction of the estimated cost of 1.9m yen (just under £10,000) per home.

Potentially the biggest problem is complacency. Every September, Japan's 124 million citizens are reminded to check their homes for signs of decay and to prepare a survival kit, including bottled water, candles and matches, a torch and a radio.

Few heed the advice.

Their nonchalance is understandable. Before 1995, they were told the chances of a major earthquake hitting Kobe were as low as 8%. Why prepare for a disaster, when no one can predict its timing, location or intensity?

As inhabitants of an archipelago that shifts, on average, once every five minutes, most Japanese do not spend much time mulling over the prospect of a catastrophe.

While their fatalism is alarming, there is little to be said, either, for living in perpetual fear of the Big One. That said, last week's quakes will have many households dusting off their survival kits - that is if they can remember where they put them.