Last month's earthquake in northern Japan was one of the biggest anywhere in the world in recent years.
Yet the fact that only one person died is perhaps a tribute to how well prepared Japanese people are for dealing with the earthquakes which frequently hit their country.
New buildings are designed to withstand the strongest tremors. The army and emergency services go through elaborate drills every year.
Japan is one of the world's most quake-prone countries
But experts predict that a massive earthquake will strike the capital Tokyo some time in the near future, and that - despite the best preparations - hundreds of thousands of buildings may collapse, and several thousand people could die.
Last month in Tokyo, there was a scene of utter chaos. Rescue teams rushed in all directions, firing up their chainsaws. In front of them lay cars crushed under piles of rubble, and crumpled houses. Helicopters hovered over badly cracked buildings.
The teams worked at speed, sawing holes in the collapsed walls, leaping in and bringing out casualties. Some seemed badly injured, some were unconscious.
But the injuries were not real.
This was Japan's National Disaster Prevention day, held every year to mark the great Kanto earthquake of 1923, which flattened Tokyo and killed more than 100,000 of its inhabitants.
This year a million people took part in the exercise. The reason they take it so seriously is that earthquakes occur all the time in this geologically unstable country - and the capital city is well overdue for a big one.
The problem is, according to Professor Keiji Doi from Tokyo University's Earthquake Research Institute, there's no way of knowing when it will happen.
"The next big earthquake in the Kanto area is very imminent according to our history of these earthquakes. But we can't tell the exact day or time. It may occur tomorrow, or next week or next month or next year, but we can't say the exact time or date," he said.
So the only thing the inhabitants of Tokyo can do is prepare. And they do.
Every day Kuroda Masayuki from the city's Fire Department gives guided tours of its Life Safety Learning Centre to groups of school children.
He explains the city's unlucky location - right above the point where three great continental plates meet and grind against each other. Then they get to feel what a major earthquake is really like on the centre's earthquake simulator.
It is a milder version of the great Kobe earthquake of 1995. All the same, the children are thrown around the mocked-up kitchen. Furniture - fortunately made of foam - tumbles on top of them.
They are supposed to make sure a door is open, and turn off the gas, but all they can do is cower under the table, with cushions on their heads.
Even on a simulator it is an unnerving sensation.
Practising for the Big One is not the only preparation Tokyo's people are making. They're also taking a long, hard look at where they live.
The job of Hiroshi Kodaira, a structural engineer, is to assess how buildings could withstand a major earthquake.
One of the people he has been helping is Toshiki Shiraishi, the owner of a beautiful old wooden house - a rarity in Tokyo these days.
The verdict was what Toshiki had feared - that without significant re-enforcement, his house could collapse.
Japan regularly prepares for natural disasters
"I've been worried about what would happen in the event of an earthquake for some time. Only recently I read in the newspaper that half of all the people who will die will be crushed under buildings. This is something I had to do," Toshiki said.
Hiroshi checked the outside walls of the house as well.
He has equipment which can tell how solid the walls are and how much moisture they contain - a complete breakdown of a building's health.
He is contracted by the local government to offer this health check to all the residents of this area.
Using a wooden model, Hiroshi explained how the house could be strengthened without disfiguring its elegant architecture.
It will not be cheap.
Fortunately Toshiki can afford the work. Thousands of other people with old houses in the city cannot. They can only hope that when the Big One does finally strike, their homes will somehow hold up.