When the Tsunami Comes

On March 5, off the coast of New Zealand, a piece of the Earth’s crust twice the size of Asia pushed, scraped and slipped under a similarly titanic mass. A sensor registered the movement and mapped the vibration.

Thousands of kilometres away, scientists in North America took note, standing by to notify authorities of potentially map-rewriting floodwaters. Hours later, the report comes in: no tsunami risk this time.

Tsunamis, a displacement of water that can flood entire coasts, are frequently caused by submarine earthquakes and landslides. And because a major earthquake fault zone lies so close to coastal British Columbia, even more advanced warning systems recently put in place likely won’t give much time to escape for people in the tsunami’s path, say experts.

“Think of a child’s pool in the backyard,” says John Cassidy, head of the earthquake seismology section at Natural Resources Canada, and an adjunct professor at the University of Victoria.

“You put a little sheet of plywood into the water and lift it,” he says. “But instead of a small pool, we’re talking about something that’s 1,000 kilometres long.”

Cassidy says that people often misunderstand tsunamis as a single large tidal wave, when in practice they are more often a series of waves, continuing for hours.

Cassidy has a knack for turning colossal events into simple analogies. This is, in some ways, the work that scientists are performing as they grapple with tsunami and earthquake preparedness: providing information in digestible, understandable and most of all actionable terms for governments and the public, both in terms of immediate response and long-term preparedness.

Tsunamis are a fact of life for people in coastal areas. An earthquake on Good Friday in 1964 not only shattered structures and lives in Anchorage, Alaska, but also triggered a tsunami that rewrote the map of Alberni and Port Alberni, B.C., ultimately leading to their merger into a single entity.

When the 1964 Alaska earthquake hit, Cassidy says, there was no tsunami warning system in place.

Today, we have both the Pacific Tsunami Warning Center, located in Hawaii, and the National Tsunami Warning Center, located in Alaska. When earthquakes happen in Alaska or Japan, Cassidy says, B.C. now has the ability to receive advanced warning about whether or not a tsunami will reach our coasts.

Those two centres are operated by the U.S. National Oceanic and Atmospheric Administration. The centres analyze earthquake and seismic data, along with readings from tide gauges and information on sea levels, to determine threats and issue alerts.

They also use the DART — or “Deep-ocean Assessment and Recording of Tsunamis” — system.

“Those are deep ocean sensors,” says Summer Ohlendorf, science officer at the National Tsunami Warning Center. “Those are often our first measurements of a wave before it arrives at a coast.”

Ohlendorf and her fellow scientists at the centre monitor seismic data and sea level estimations 24 hours a day, along with their sister centre in Hawaii. Two scientists are always on-duty at the warning centre, looking for large seismic events that could trigger tsunamis.

The area the National Tsunami Warning Center covers is huge, spanning the east and west coasts of Canada and the United States.

Sometimes, despite monitoring, coastal communities will not receive much advance warning about tsunamis. While undersea seismic activity near Japan or New Zealand offers hours of advance time to analyze data for tsunamis hitting the U.S. or Canada, quakes much closer to home, like in the Cascadia Subduction Zone off the coast of Vancouver Island, offer little to no advance notification.

“We can give people maybe 20 minutes of warning if a quake is right off the coast,” says Ohlendorf. “If you don’t have your bags packed and a plan and know where to go, 20 minutes doesn’t seem like a whole lot of time all of a sudden.”

One seismic monitoring centre in British Columbia that supplies data to the NOAA is the earthquake early warning system operated by Ocean Networks Canada, a non-profit society funded by the Canada Foundation for Innovation through the University of Victoria.

This early warning system was installed in June 2019, with seismic sensors placed throughout Vancouver Island and the Juan de Fuca tectonic plate.

The purpose of the system is less about providing large-scale public notification than it is about protecting vital infrastructure. With earthquakes in immediate proximity to B.C.’s capital and economic hubs, the early warning system will provide an advance notice of as little as 60 to 90 seconds.

Benoît Pirenne, director of user engagement with Ocean Networks Canada, says those seconds can be vital.

“A typical example would be the SkyTrain in Vancouver,” Pirenne says. “If you know there’s shaking coming and you know there’s about a minute of time for you to act, then it may be sufficient time to bring the train to the nearest station and not get stuck in the middle of a tunnel.”

The advance warning can also be issued to emergency services, allowing them to ensure vehicle bay doors are open in case they are rendered inoperative by shaking damage.

However, Pirenne says that Ocean Networks Canada’s tsunami studies don’t begin and end with immediate response. Advance planning can be key as well.

The data that the centre, NOAA and other organizations collect is being used to model geographical problem areas. This can inform civic planning and emergency evacuation for governments.

Scientists are also learning from historical information. Indigenous oral history says the last time a mega-tsunami struck the province was around 1700, wiping out entire villages on the west coast.

These accounts were further corroborated by contemporaneous records from Japan that pinpointed this massive Cascadia Subduction Zone earthquake to 9 p.m. on Jan. 26, 1700.

Over 300 years later, scientists at Ocean Networks Canada are now testing a prototype radar system, recently installed in Tofino, which could detect incoming waves up to 80 kilometres away. This system, Pirenne says, could allow an immediate warning in communities like Tofino and Ucluelet, offering an advance of a few short, but vital, minutes.

More importantly, it could detect meteotsunamis, which are caused by changes in atmospheric pressure instead of landslides or earthquakes. Scientists are only just beginning to understand these specific types of tsunamis and how to forecast them.

All of this centuries-spanning knowledge contributes at a global level to reduce the damage and loss of life of tsunamis. But in order to take advantage of advances scientists have made, governments and the public need to prepare, too, by bolstering emergency response systems, maintaining emergency response kits and developing emergency response plans, something only 13 per cent of B.C. households currently do.

Tsunamis are an inevitability; we know that the “really big one” is coming.

At the Museum of Anthropology in Vancouver, an exhibition on the 2012 tsunami shows us what’s at stake: a country transformed by the roar of an ocean forced onto land by the might of the planet.

The quake near New Zealand on March 5 did not generate a tsunami. The next one may.

Our scientists will be there to watch, and wait, and inform us.