Distance was no barrier to Ocean Networks Canada’s (ONC) capacity to provide real-time critical data about the tsunami risk following an underwater volcano eruption in Tonga on Saturday, 15 January 2022. Nine thousand kilometres from the volcano, the ONC offshore sensors gathered a variety of data, informing the National Oceanic and Atmospheric Administration’s Pacific Tsunami Warning Center alerts that go out to countries and territories in the Pacific and Caribbean regions.

This map of ONC's offshore NEPTUNE cabled networks shows arrival times of the tsunami waves caused by the Tonga volcano. Tsunami waves travel at ~800 kilometres per hour, the speed of a jet plane.

The tsunami’s eastward progress across the Pacific Ocean was tracked in real time by ONC’s bottom pressure recorders, using our sophisticated data management portal Oceans 2.0. This timely data provides critical ocean intelligence about wave heights, and informs official tsunami alerts to the public. Additional real-time wave height, ocean surface current and wind direction data are provided by high resolution coastal radars, including a state-of the art WERA over the horizon radar system in Tofino. These #knowtheocean data not only allow emergency services to activate safety protocols ahead of tsunami impacts, they also support future tsunami modelling and research.

Bottom pressure recorder data from ONC’s offshore NEPTUNE sensors show tsunami wave arrival times on Saturday, 15 January 2022.

“Tsunamis generated from undersea volcanos are rare, and measurements of the waves generated are even rarer,” says Kate Moran, president and CEO of ONC. “These data will be used to understand the risk of these types of ocean events.”

While the volcanic eruption in Tonga was not caused by an earthquake, the vibration registered the equivalent of an M5.8 quake on our seismic sensors.

Air pressure changes

Tonga's Hunga Tonga volcano just had one of the most violent volcano eruptions ever captured on satellite. pic.twitter.com/M2D2j52gNn

— US StormWatch (@US_Stormwatch) January 15, 2022

The shockwave caused by the violent Tonga volcano travelled around the globe three times and was reported around the world—as far away as the UK—producing changes in the barometric pressure for several minutes.

The volcano’s shockwave was recorded by ONC community observatories’ weather stations on the British Columbia coast. Notice the coincident blip shortly after 12.00.00 UTC at all locations.

Tsunami inundation studies

In addition to real-time monitoring, ONC supports tsunami resilience in at-risk coastal communities by integrating high resolution data and detailed geographic mapping into models for public safety.

This high-resolution land-river-sea digital elevation map (DEM) of the cross-border Salish Sea region reveals the complex geographic features that influence the behaviour of tsunami waves and currents as they move towards and impact the densely populated Vancouver lower mainland.

Since 2016, ONC has been involved with tsunami inundation and sea level rise studies for at-risk communities along the coast, including Port Alberni, Tofino, the Salish Sea, Prince Rupert, Haida Gwaii, and the Strathcona Regional District. In collaboration with government agencies, First Nations communities, and engineering companies, these projects inform local emergency planning efforts. Cutting edge science and engineering principles are coupled with Indigenous community engagement, seeking input from the local population and gathering historical knowledge of past tsunami events.

"We are grateful that our Strathcona Regional District coastlines did not experience any direct impacts of the Tonga tsunami, but it highlighted the critical value and urgency of the tsunami inundation project that is currently underway by Ocean Networks Canada and Northwest Hydraulic Consultants", comments Shaun Koopman, Strathcona Regional District Protective Services Coordinator.

Like many regions on British Columbia’s coast, the Strathcona Regional District is considered highly vulnerable to tsunami events originating either from a large earthquake triggered in the Cascadia subduction zone offshore Vancouver Island, or one from the Alaska-Aleutian subduction zone to the north. ONC is currently working in partnership with local coastal engineering firm Northwest Hydraulic Consultants to support regional government, First Nations

“These tsunami inundation projects are a collaborative effort to understand which areas are most at risk, how soon the waves will impact the coast after an event, how high those waves may be and how fast we expect them to be moving,” says Gord Rees, ONC associate director, applied science solutions. “This information is crucial for identifying where the safety boundaries are, allowing emergency planners to work with their communities to ensure that appropriate emergency response plans are in place.”

Be tsunami prepared

Tsunamis are most often caused by undersea earthquakes that cause large waves. It may take hours for waves to reach the shore if an earthquake happens far away. Strong earthquakes near land could generate a tsunami that arrives onshore in less than 20 minutes.

A few sites for further information:

• Emergency Management British Columbia
• Capital Regional District
• Strathcona Regional District – Tsunami Resources & Maps
• Port Alberni Regional District
• Tofino
• British Columbia Tsunami Notification Zones
• Understand what the alerts mean: Watch, Advisory or Warning?

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Listen to ONC President and CEO Kate Moran talk to CBC On the Island about the tsunami

Tsunami monitoring and public safety for at-risk communities