Here's how one of B.C.'s top tourism destinations would fare in an earthquake

How would one of B.C.’s most iconic coastal locations fare in the event of an earthquake?

Katsuichiro Goda, a professor at Western University and a Canada research chair in multi-hazard risk assessment, recently published a paper examining the tsunami and earthquake risk for Tofino, looking to answer that question.

While a city like Vancouver would face serious impacts if an earthquake occurred, it has the benefit of being sheltered by Vancouver Island, which would protect it from the worst of a tsunami.

Tofino, however, does not have this luxury. Not only is it on Vancouver Island, but it also faces the Pacific Ocean and the Cascadia Subduction Zone, where the Juan de Fuca Plate is slowly sliding under the North American Plate. As these two tectonic plates push against each other, they create built-up stress. When that stress becomes too much, an earthquake happens. 

Goda said Tofino would suffer from both the shaking caused by the earthquake and a subsequent tsunami.

What would happen in the event of an earthquake and a tsunami?

Goda analyzed 5,000 different cases in his analysis, ranging from low risk to high risk, and then assigned how likely those estimates would be. He emphasized that his analysis captures the range of uncertainty.

What he found is that while both the tsunami and shaking could cause economic consequences, a tsunami is likely to cause the most deaths.

Given that Tofino is relatively flat along its beaches, it could take someone 20 to 30 minutes to reach 10 metres and above. But the amount of time someone has to evacuate before a tsunami might strike could be a mere 15 to 30 minutes.

In the most extreme case, Goda said that between 400 and 750 lives might be lost due to a combination of both human and natural factors. For example, this could occur if a tsunami happened at night (when people were less likely to evacuate) and the plates slipped right off Vancouver Island, rather than somewhere further south on the Cascadia Subduction Zone.

But Goda said that this is about a one in a million shot, like getting hit by lightning.

“The typical case could be much, much significantly less.”

He said that there is roughly an 80 per cent chance that fewer than a hundred people would die. 

“The uncertainty is so large, so [looking at] only the mean or the only extreme situation doesn’t capture the whole thing. We shouldn’t consider what will be the five per cent chance, or what will be the average case, or what would be the 95 per cent chance,” he said.

What else is at risk?

Goda’s analysis also looked at Tofino’s $2.2 billion in assets, which includes all of its hotels and residential buildings.

While Tofino’s commercial area is 20 metres above sea level and doesn’t face the Pacific Ocean directly, the low-lying beach areas with houses, hotels, and campsites are at much greater risk, given that they face the Pacific Ocean directly.

This accounts for about 45 per cent — or $1 billion — of that is in the low-lying areas of Tofino, which are at risk of getting hit by a tsunami.

While buildings can be built seismically to withstand an earthquake’s shaking, there isn’t much that can be done to prevent them from getting damaged if a tsunami hits them.

“The water height pressure is so high, and then the building simply cannot withstand it,” Goda said. “The ground is shaking more like a vibration. Some structures do well, and some structures don’t do well.”

But he said it’s people’s choice to build in a tsunami zone.

“Well, the building owners want to enjoy the beautiful scenes, and then nice access to the beaches, and so on. Then they have to build a right on the coast, but unfortunately, there is the Cascadia Subduction Zone.”

What can be done?

Goda hopes this research can motivate people to reduce risk from both earthquakes and tsunamis.

Already, Tofino has some systems in place to alert people about tsunamis: an alert system that people can sign up for, as well as sirens on the beaches.

On the District’s website, it states that people should also be aware of natural warning signs, since there might not be time for an official warning if a local earthquake occurs. These include prolonged shaking, strange ocean behaviour, sudden recession of water, or a loud ocean roar.

If this occurs, people should evacuate to high ground immediately.

Goda also suggested building vertical evacuation structures in coastal beach areas, giving people direct access to elevated structures in the event of a tsunami.