Now we know what it will look like.
The earth's crust fractures, the ground shakes and a deluge of water pushes far inland. In its wake, parts of Japan look like the wreckage from an epic Godzilla v. Mothra rampage.
Elsewhere, a stone facade collapses, transforming the face of a century-old building into a doll house in which you could see the interiors of rooms. A car is crushed beneath fallen masonry. A green, copper-topped dome smashes onto the ground.
One of the buildings severely damaged in last month's earthquake in New Zealand was the Cathedral of the Blessed Sacrament in Christchurch. Two bell towers collapsed, destroying vehicles parked below.
The Basilica, as it is known, underwent a seismic retrofitting seven years ago. An earthquake last September weakened the structure, so the doors were closed to the public and religious services were moved elsewhere. No one was killed by the building last month.
For those of us living in Victoria, the pictures of the damaged, neo-classical building caused a chill.
It looked like our 113-year-old Parliament Building had collapsed.
The Old Rockpile is in danger of suffering significant damage in a serious earthquake, according to a report released in recent days. Walls of unreinforced brick and masonry are brittle, while the copper roof is in disrepair. The bill for a seismic upgrade - a quarter-billion dollars.
Meanwhile, the three-story, red-brick Armoury building on the Legislature grounds facing Menzies Street is in an even worse state of disrepair and has been described as a possible "death trap" even in a modest earthquake.
This has given rise to black humour among reporters. One quipped that his emergency kit consists of a loaded revolver and a bottle of scotch.
That's not to mention the neighbouring Empress Hotel, built atop landfill in an area that appears on government maps as being at high risk for amplification and liquefaction. The doom-and-gloom scenarios will seem more real with the publication next month of Cascadia's Fault (HarperCollins), a non-fiction book by the independent filmmaker Jerry Thompson. He examines the outcome should a catastrophic earthquake of 9.0 - or, gulp, worse - on the Richter scale strike along the 1,100-kilometre stretch of the offshore Cascadia Subduction Zone.
It has happened once before in recorded history, around 9:30 p.m. on Jan. 26, 1700, when a powerful earthquake caused the ground to drop almost two metres below sea level along sections of the coast. The event was recorded in Japan the following day as a destructive tsunami.
Many places along western Vancouver Island are vulnerable to a tsunami, including Port Alberni, which suffered heavy damage when a two-story tall wall of water generated by an earthquake in far-off Alaska came roaring down the inlet.
"Imagine that Cascadia lifts up a wave just 15 minutes off shore and it comes down that canyon," Mr. Thompson said.
"Tofino has very little high ground. There are some places to escape to, but you have to know where to look."
"Ucluelet is better off. The high school is on the highest piece of ground there and everyone knows to rendezvous there."
His research also shows a tsunami could roar along the Juan de Fuca Strait, causing devastation at Bellingham, Wash.
If Vancouver is heavily damaged, the metropolis will get much of the available aid, he said. Places on Vancouver Island, especially those that are isolated, will have to make do.
"Everyone's going to be on their own for a long time," he said.
Mr. Thompson said all of us on the West Coast can learn a lesson from Tilly Smith. The 10-year-old English schoolgirl was with her family on the beach in Thailand when she became hysterical at the sight of a frothing sea. She had just learned about the phenomenon in her Grade 6 geography class - this was a warning sign that an underwater earthquake had generated a tsunami. The family fled to their resort hotel, scrambling to safety on the third floor as the first of three waves rushed in.
They survived because an elementary student paid attention in class and knew what to do. So should we all.