This is part three of a special eight-part report done by Black Press Media on emergency preparedness in Greater Victoria. Find the series online at vicnews.com/tag/greater-victoria-emergency-preparedness
When a tsunami strikes will you be ready?
In March 2011, a 9.1 magnitude earthquake near Japan triggered a tsunami with waves that surged to heights of up to 130 feet (40 metres). It killed nearly 20,000 people and caused a major nuclear meltdown. This event is similar to what can be expected from the Cascadia Subduction Zone, which stretches from northern California to northern Vancouver Island, according to Washington State’s emergency management division.
But unlike some areas in Washington, “we don’t face the open ocean … we’re somewhat sheltered,” explained Geoff Amy, Colwood’s emergency program coordinator. “The threat varies from area to area … We do not, according to the scientists, have a threat or a major threat from a distant earthquake.”
The 2011 earthquake near Japan resulted in 15-centimetres waves in Colwood, with the most noticeable changes being to ocean currents, Amy said.
There are two types of tsunamis that could strike the region – local and distant. A local tsunami is associated with a ‘felt’ earthquake and a distant tsunami will originate far away and the earthquake may not be felt.
A tsunami is a series of long waves caused by a sudden shift in water triggered by an event such as an earthquake, landslide, volcanic eruption or explosion. The speed in which a tsunami travels is dependent on the depth of water. In deep oceans, a tsunami is barely noticeable but can travel at speeds upwards of 800 kilometres per hour. The closer it gets to shore, the higher the waves get and they begin to slow to speeds of 30 to 50 km/h.
But in 2018, a 7.9 magnitude earthquake in Alaska did trigger a tsunami warning for Greater Victoria, much to the surprise of local emergency programs coordinators.
In 2013, the Capital Regional District (CRD) conducted tsunami modelling, but it was based on an almost worst-case scenario, explained Tanya Patterson, the City of Victoria’s emergency program coordinator. Teams are working to update the modelling to include lesser threats, such as the 2018 earthquake which was believed and proven to be of minimal risk to Greater Victoria.
During the 2018 warning, 276 911 calls were made locally “and that was in the middle of the night,” said Sarah Hunn, Victoria’s emergency management community liaison. “People were calling 911 to ask about the tsunami … it’s not a means to get information,” she emphasised. “We see in other disasters the 911 system get overloaded and crash.”
Which means people in life and death situations cannot get the help they need.
Many residents also jumped into their vehicles and fled to higher ground, whether that was the top of a local mountain or the Malahat.
“People weren’t identifying what high ground was,” Amy explained. “You don’t need to go very far up Lagoon Road [in Colwood].”
A sentiment echoed by Patterson. “The public’s understanding of our risk wasn’t there and that’s what we’ve been working on.”
In the event of a magnitude 9 earthquake along the Cascadia Subduction Zone, the CRD predicts a tsunami will reach Port Renfrew in approximately 35 minutes with wave heights of up to 11.5 feet (3.5 metres), followed by Sooke Harbour within 60 minutes with waves of over eight feet (2.5 metres) and the Esquimalt and Victoria harbours in 76 minutes with respective wave heights of nearly nine feet (2.7 metres) and eight feet (2.5 metres). It will then reach Cadboro Bay within 90 minutes and Sidney within 110 minutes, with both expected to see waves up to 6.6 feet (two metres).
The CRD considers four metres – 13 feet above sea level – to be a safe distance.
Amy noted residents looking for more information should go to their municipality’s website or attend an emergency preparedness seminar. Different areas also offer alert systems for residents to subscribe to.
After the 2018 warning, the City of Victoria’s alert system went from approximately 6,000 subscribers to 60,000 within a week.
British Columbia’s tsunami notification zones
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