Somewhere deep beneath Tinakori Rd, rock buckles under grinding pressure. The shockwaves ripple through ground, hitting buildings, roads and pipes with a sharp but enduring judder.
In Wellington about 200 buildings from small shops to high rises are severely damaged, some of them collapsing completely. Along Cuba St, and Riddiford St in Newtown, unreinforced masonry buildings spill their guts onto the pavement below. Three cars, waiting for the lights to turn green, are buried.
With gas pipes ruptured, fires break out. People fight the flames but, with the water mains sustaining more than 5000 breaks across the system, the taps quickly run dry.
The waterfront promenade built on reclaimed land sinks metres into bubbling liquefied silt. Te Papa and Westpac Stadium survive but on a tilt, as if sitting on the deck of a sinking ship.
It is estimated up to 1500 people will be killed if a big quake strikes Wellington, and another 12,000 could be injured, most of them in the central city. Wellington civil defence emergency management regional manager Bruce Pepperell says that, in the first hours, people should not expect help.
Police, fire and the hospital will be facing their own disruptions, particularly around access. The closest national emergency response team is in Palmerston North, which will take at least 12 hours to get geared up and get into Wellington.
"Ninety per cent of rescues will be done by people on the street," Mr Pepperell says.
Urban Search and Rescue, fire and paramedics should be helping people within the first 24 hours, but rescue efforts could be hampered by lack of access and water.
Some parts of downtown Wellington could be flooded, and other suburbs be cut off by slips and collapsed roads. Paramedics may end up roaming suburbs on foot, treating people as they find them.
All roads in and out of Wellington city are likely to be buried under slips, most of them for weeks if not months. The city, Porirua and the Hutt Valley could be cut off from one another, and from the rest of New Zealand. Many of Wellington's hilly suburbs could effectively become islands.
While a massive national response machine grinds into action, tens of thousands of Wellingtonians could see nobody official for days, if not weeks. They will be reliant on friends, family and neighbours - if they can reach them - and whatever they have stored in their homes.
Mr Pepperell says the initial focus will be on rescuing people and evacuating the worst injured. People who survive physically will have to make do.
"The first few days we will be more concerned with life and limb. We are not going to be focused on bringing water tankers around to someone who hasn't made their arrangements."
Wellington sources the vast majority of its food from outside the region, and supermarkets store only enough for three days' supply.
When emergency supplies start trickling in, it will be in dribs and drabs. Hercules transport planes from Ohakea could fly over cut-off communities, dropping supplies by parachute. A few all-terrain army vehicles could go off-road to reach people, but would be able to carry only limited supplies. "There are a lot of goat tracks that can be made navigable," Mr Pepperell says.
It would take at least four days to ship in large quantities of fresh water and food, probably using barges landing in Wellington Harbour.
Before the first barge lands, it is estimated that, collectively, Wellingtonians will need to find 10.5 million litres of water and more than 1000 tonnes of food. Every drink bottle and spaghetti can will count.
There are no plans for mass evacuation, although if it proves too difficult to get food and water into the region, that could change.
Mr Pepperell expects most people will be able to continue to live in their homes. "If they are prepared in their homes, it is going to make such a difference."
Transport in and out of Wellington Airport will focus foremost on getting vital medical supplies and personnel into the region, and flying out people with immediately life-threatening injuries.
The next priority is to get "critical government staff" - such as the prime minister - out of Wellington, followed by people with less pressing injuries.
About 50,000 Wellingtonians could be displaced by the quake, their homes destroyed or inaccessible. By the end of the second day, welfare centres should be operating in some areas but the first choices, Te Papa and Westpac Stadium, may be deemed unsafe. Many people working and living downtown are expected to gather at the Basin Reserve. Others will huddle in parks and the town belt.
In the suburbs, schools and community halls - the ones still standing - will become default gathering places and eventually welfare centres.
For weeks, there will be no power, gas, water or sewerage and, in some areas, these services may not be restored for months.
Unlike Christchurch, the undulating topography in Wellington will make it almost impossible to cordon off the CBD. Shattered access routes will have to work around demolition sites for years, as about 2.5 million tonnes of rubble is pulled out of the CBD and dumped near the railway station.
While it will be a time of devastation, it will also strengthen communities. People may rely for their survival on neighbours they have never met, end up helping strangers or discover a knack for digging long-drop toilets.
With preparation, the shaken city will survive, Mr Pepperell says. "If people just start to take some simple precautions it is going to make a huge difference."
This is based on several Civil Defence reports, interviews and simulation of what could occur in a magnitude 7.5 quake on the Wellington fault. It assumes there will be no tsunami, although that is possible in quakes of such size. There is a less than 10 per cent chance of a 7.5 quake occurring on the Wellington fault in the next century.
- © Fairfax NZ News