Some time in the next few decades, the Indonesian city of Padang will cop the ''big one'', an earthquake in the Sunda Trench 200 kilometres offshore with enough power to bring into being a tsunami 20 metres high.
Within 30 minutes the wall of water will have hit the shore. It will cross the beach and flood onto a coastal plain that houses a million people, 300,000 of them living fewer than five metres above sea level, mostly in single-storey dwellings.
Many buildings will already be damaged from an earthquake geologists say could register magnitude 8.8, the earth vibrated into liquid and the roads rendered impassable. The wave will pick up this debris and use it to scour the landscape.
The wave will travel a kilometre inland, even further along the three rivers that drain water from the mountains to the sea.
We know this because the massive fault line that lies just off Padang is one of the most intensely studied in the world. It's where the Indo-Australian tectonic plate, which is moving north, collides with the Sunda plate and passes underneath it. For 200 years since the last big one in 1797, in a spot just off Padang, one area has been ''stuck'', with pressure building.
Smaller earthquakes in the area, including one in 2009 that killed 1200 people in Padang, have only increased that pressure. When it suddenly comes ''unstuck'' - a process due to happen about now - the damage will be catastrophic.
''In geological terms, it's imminent,'' says Trevor Dhu, the risk and vulnerability manager at the Australia-Indonesian Facility for Disaster Reduction.
So with all this advance notice, surely the people of Padang are prepared? The answer, in short, is no.
A recent visit to this city on the edge of disaster revealed that its residents have neither the ''hardware'' - safe buildings and places to evacuate to - nor the ''software'' - education and knowledge - to survive the coming catastrophe.
The Australian aid program AusAID, with the Indonesian government, are trying to provide both, but in the face of massive ignorance, poverty and occasionally superstition, it's an uphill battle.
The lack of knowledge, or even conversation, about earthquakes, is striking considering the danger.
Eric Kurniawan is training to be a dentist, so is better educated than most of Padang's residents. But when I showed him an inundation map of his city, he visibly blanched. It was the first he had heard of the danger of earthquake and tsunami.
Kurniawan's family live deep in the ''red'' zone, but he had no idea of the risk, nor what to do if a big wave came.
Weeks after we met he contacted me again, saying: ''I am scared.''
''In certain areas people still believe that, if you talk about a tsunami, it will happen,'' says Patra, an organiser with local disaster education group Kogami. She is trying to get earthquake safety put on the region's school curriculum, but is frustrated by a lack of interest at the government level. They say the children already have enough to learn.
The SDN 02 Lubung Alung school is north of the city and out of the tsunami zone, but it's still well within the range of an earthquake.
Principal Zulbaiti Kamil boasts that the children have done an evacuation drill ''already 10 times'' since the 2009 quake. But ask the children what they would do if their building shook and their faces go blank. Finally one little girl, Maulidian Nurul, ventures: ''We have to get out of the building to an open field.''
She's right, but she seems to be the only one who knows, even though many of the children still live in the remnants of homes damaged by an earthquake three years ago.
The 2009 quake was too deep to be the big one, and did not happen in the heart of the fault line. But it killed 1200 people and severely damaged or destroyed about 140,000 houses and 4000 other buildings.
Further down the road from the school, young farmer Yaldi is bending 10mm-diameter reinforcing wire into shape. Yaldi lives with his mother, Sias, 56, and younger sister, Yeni, 15. With the help of AusAID he is rebuilding his home to withstand the coming temblor.
''It's a safety house. A quake safety home,'' he says, demonstrating how the wire reinforcing goes into the building's concrete substructure.
The family house was severely damaged in 2009 and his mother was traumatised. They lived in a tent for a while, and then moved back into the damaged building, avoiding the most unstable rooms, until they could afford to rebuild.
The house next door is also being rebuilt. But it looks decidedly less sturdy. It is owned by Yaldi's aunt, Pik Manih, his mother's sister.
In Padang's matrilineal society it is the women who own the land, and these sisters live on the land once owned by their mother.
At Pik's house, her husband has made attempts at reinforcement, but the wire is too thin, the bracing too far apart. The roof simply sits atop the walls, without being joined as it should be; one wall is made of unstable river stones set in mortar.
Pik says ''of course'' she is worried that the new house will fall down in an earthquake, as the old one did.
''It's not finished yet and we're still living in a wooden house behind this one, but … even when we've completed this one, it doesn't feel any safer.'' Building an earthquake-safer house is more expensive and takes more skill than building in the old style. Aid helps educate people in how to ''build back better'', and provides grants based on individuals meeting performance targets.
But many ignore the advice, rebuilding using cheaper methods.
A report commissioned by AusAID found last year that ''there is a high level of indifference for, and no social or political pressure for promoting or supporting, safer building techniques''.
Six construction techniques are needed for better housing, and most in Padang had applied none of them. Only eight out of 3000 family heads interviewed had applied all six.
''The most mentioned barrier to building safely is lack of money,'' the report found. Most people in this poor country had little money and what they saved went to school fees.
Patra, at local organisation Kogami, said the most important safety measure is education, and the biggest barrier is the ''mindset of the government''.
''Instead of having a government program, we have to go from one school to another, talking to each principal, to convince them to put in place the curriculum,'' she says.
Of the 200 schools in the ''red zone'' her group has visited perhaps 70.
Indonesia is one of the most disaster-prone nations on earth, but disaster management is a relatively recent concern.
Jason Brown, who is responsible for training and outreach at the Australia-Indonesian Facility for Disaster Reduction, says the message is starting to get through, at least at the official level.
Indonesia's Minister for Disaster Mitigation, Syamsul Maarif, was in Padang recently outlining the new masterplan and said it included an ambitious scheme to build ''vertical evacuation'' high structures on the coastal plain that people can go up to avoid inundation in a tsunami.With 2000 to 3000 people per shelter, Mr Syamsul says the government would need to build about 150 shelters.
He also recognises the need for education, and says funding for these measures will become available in next year's national budget.
But in a land where ignorance is bliss and promises often exceed delivery, the people of Padang should hope that the big one does not hit quite yet.