Tsunamis in Canada

Tsunami damage in Port Alberni, BC after the March 28, 1964, magnitude 9.2 Alaskan earthquake. Photo credit: Natural Resources Canada

For more info on tsunamis

• Atlas of Canada - Natural hazards - Tsunamis
• Oceans and Fisheries - Tsunamis and Tsunamis Research

Tsunamis are a series of large waves that strike coastal areas. They can happen with little warning and result in flooding and damage to coastal communities. Thankfully, they are a rare event. Storm surges are more common. Residents, particularly those living in low-lying areas near the coastline, should prepare in advance.

• Tsunami facts
• How to prepare for a tsunami
• Early warning signs of a tsunami
• What to do when a tsunami hits
• Include this page in your emergency plan

Tsunami facts

• Tsunamis are a series of large waves caused by events such as submarine earthquakes, landslides, volcanic eruptions, and less commonly, meteoric impacts. Tsunamis can also occur in large lakes.
• They can occur with little warning in the ocean and in lakes.
• A tsunami can be triggered by a large, high energy, but relatively short duration disturbance of the sea floor. Such waves can travel across the ocean at high speed (800 km/h, the speed of a jet plane).
• As the tsunami waves approach the shoreline and water depth shallows, the wave speed slows, but wave height will increase as wave length decreases. In 20 m of water, wave speed will be 50 km/h.
• Tsunamis can occur as individual or multiple waves following each other by minutes and even hours.
• Tsunamis can grow to 60 or more metres in height (the size of a ten-story building).

How to prepare for a tsunami

• Check your house and land for any potential dangers related to flooding.
• Identify any vulnerability and repair it.
• Learn how to turn off the gas and electricity in your house. Local authorities may instruct you to shut these off.
• Do not store your important documents in the basement. Keep them at a higher level, protected from flood damage.
• Ensure that your family has an emergency kit and plan.
• Ensure the emergency kit is portable, in a back-pack or suitcase with wheels.
• Your local chapter of St. John Ambulance can teach you first aid and CPR. Your local Red Cross can teach you survival techniques in the water through their swimming and boating courses.

If you have any questions or need to know more about evacuation procedures, contact your local emergency management organization, or police or fire department.

Early warning signs of a tsunami

• One of the signs of a potential tsunami is the occurrence of a very large earthquake that lasts for more than 20 seconds. If an area has been shaken by a very large earthquake, one should be on alert that shorelines located within the radius of the earthquake's epicentre, may be hit by a tsunami.
• A more immediate and ominous sign of an approaching tsunami is a rapid and unexpected recession of water levels below the expected low tide. This can occur minutes before the shoreline is struck by a tsunami and can be the only sign along coastlines that are located too far from the earthquake epicentre to have felt the shaking.
• A tsunami may also occur with very little warning.
• Natural Resources Canada's seismologists monitor for such events, around the clock. As soon as possible, a tsunami warning is issued to media and municipalities in regions where a tsunami is likely to hit.
• The Canadian Coast Guard's Marine Communications Traffic Services broadcasts tsunami alerts to mariners.
• When you get warning of a tsunami, if there is time, move to higher ground immediately.

What to do when a tsunami hits

• Do not go near the shore to watch a tsunami hit. If you can see it, you are too close to escape.
• Should a tsunami occur and you cannot get to higher ground, stay inside where you are protected from the water. It's best to be on the landward side of the house, away from windows.
• Often tsunamis occur in multiple waves that can occur minutes apart, but also as much as one hour apart.
• Monitor the tsunami's progress and listen for warnings or instructions from local officials. If you are safe when the first tsunami hits, stay put until authorities declare all is safe.
• After a tsunami hits, you may encounter flood waters. Flood waters can be dangerous to walk or drive through. Before driving anywhere, it is best to listen carefully to rescue officials who will be coordinating evacuation plans.
• Be aware of risks such as hypothermia from cold water or drowning from running water. Your local chapter of St. John Ambulance or Red Cross can provide more information on how to prevent these problems.

Include this page in your emergency plan

If you live on any of the coastal areas of Canada, print this information and include copies in your emergency plan and emergency kit.