Predictions: How Did the ‘Major’ Earthquake Hit the Pacific Northwest?

“Your phone is ringing”Earthquake!” The voice tells you to duck, cover and hold on. After about 30 seconds, the tremor begins.

At first it causes the furniture to shake. Stronger than the smaller earthquakes you normally encounter here Seattle. After 30 seconds, the shaking suddenly intensifies.

Pictures fall off the walls, objects fly across the room, and the dining table you’re sheltering under begins to slide across the floor, a few inches at a time.

A loud hum fills the air. this sound buildings of the city it shakes, it squeaks, and its entire contents shake, wobble, scrape against the floor, or fall off the shelves.

Seattle ain’t even that near the epicenter of the earthquake.

The Olympic Mountains stand about 100 miles between the city and the ocean. For people on the coast, the shaking is much worse.

“It will be the worst natural disaster our country has ever seen.”
Robert Ezelle, director of emergency management at the Washington state Military Department

After about six minutes, the earthquake ends and a new countdown begins. People on the shore now have 10 to 30 minutes to reach high ground before a giant wave engulfs the shore. Pacific Northwest.

Tsunami sirens sound in some cities. In others, it disabled earthquake warning systems.

An eight-storey-high wall of water is rising towards the coast from Northern California to Vancouver Island.

In the next hour or two, tsunami It moves through rivers and straits into Puget Sound. When it reached Seattle it was much smaller, but some streets were flooded.

Between earthquake and tsunami14,000 people died, many more were trapped or injured, and more than 618,000 buildings damaged. The tremors triggered landslides, fires and spills of hazardous materials.

But the disaster has just begun.

Eventually, total economic losses will reach $134 billion, placing it at the top among the costliest countries. natural disasters in US history.

The scene above shows the worst-case scenario of a mega-earthquake hitting the Pacific Northwest. Emergency managers have spent decades preparing for this. Still, they say the region isn’t ready.

“It’s impossible to be completely, completely, completely prepared because of the magnitude of the event,” Robert Ezelle, director of the Washington state Military Department’s emergency management division, told Business Insider.

Inside the looming catastrophe on the Pacific Northwest coast

Deep beneath the seafloor, about 100 miles off the Pacific Northwest, two tectonic plates They create tensions that can explode at any moment.

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In a region called Cascadia subduction zoneThe Juan de Fuca oceanic plate is slipping (or “sinking”) beneath the North American plate—but its edge remains stuck. The stress increases as the plate continues to press against its locked edge.

“It’s been alarmingly quiet,” Harold Tobin, a Washington state seismologist and director of the Pacific Northwest Seismic Network, told BI. “The fact that it does not create even very small earthquakes leads us to believe that it is completely locked.”

Scientists like Tobin fear that without reducing stress through smaller earthquakes, the Cascadia subduction zone is more likely to explode in a “megathrust” earthquake. mega earthquake In short, it is about size 9.

“This will be the worst natural disaster our country has ever seen,” Ezelle said. That’s why some call him “The Big One.”

On average, the Cascadia subduction zone produces a very large earthquake every 200 to 500 years. The most recent was in 1700.

How big is the Big One?

The Richter scale, which measures the magnitude of an earthquake, is logarithmic, not linear. This means that a magnitude 9 earthquake releases approximately 32 times as much energy as a magnitude 8 earthquake and approximately one million times as much energy as a magnitude 5 earthquake.

Closest thing to the Great One in human memory Occurred in Japan in 2011. The magnitude 9 event, called the Tohoku earthquake, also came from a subduction zone.

It created a tsunami that reached heights of 130 feet, submerged more than 1,200 miles of coastline and swept thousands of people out to sea. The earthquake and tsunami together killed an estimated 18,500 people.

It’s hard to imagine the power of a magnitude 9 earthquake, but Seismic Sound LaboratoryA group of scientists from Columbia University prepared a video that tried to convey this through sound.

The animated video below shows every earthquake that occurred in Japan from 2008 to 2014, along with various sound levels. A normal background hum of magnitudes 4, 5 and 6 gives way to an intensely loud explosion, the Tohoku event, in about 22 seconds. (The label stating that the incident occurred in 2012 is incorrect.)

Years after the Tohoku incident, aftershocks It rippled across Japan, increasing damage including a 7.1 magnitude earthquake in 2021.

Similarly, in the Pacific Northwest, aftershocks can continue for months, perhaps even years, after the Great Earthquake. The first tsunami may not have been the biggest.

Those who came after the Great One

Scientists, Ezelle’s department and the Federal Emergency Management Agency have practiced for the Big One in two “Cascadia Rising” exercises, one in 2016 and the other in 2022.

“The people we trust as first responders may very well become victims.”

They found that much of Western Oregon and Washington may have collapsed in the days following the megaquake. without electricityinternet, cell phone service or drinking water.

In some areas, it may take more than two weeks for help to arrive due to landslides. sinkholesBridge collapses and other damage to roads can make travel impossible.

both Oregon and Washington recommends that all residents have at least enough food, water, and medicine two weeks.

“The people we hope will be first responders “There may very well be victims,” ​​Ezelle said. “A lot of them will be neighbors taking care of neighbors.”

Among the dozens of readiness objectives identified after the last Cascadia Ascension exercise, Ezelle’s division is assessing the state’s roads to determine “lifelines” between mountains; that could combine surviving or quick-to-repair routes to transport critical supplies to shore.

Once these lifelines are opened after a mega-earthquake, national and international aid can be activated. A FEMA spokesperson said in an email to BI that the agency will have teams ready to respond “almost immediately.”

Reinforcement of old buildings It is also very important because many of them are not resistant to mega earthquakes. There isn’t much money for this “piecemeal process,” Tobin said.

“We really have a long way to go,” he added.

Japan has been aware of the risk of giant earthquakes and tsunamis for centuries. His One of the most prepared nations in the world. And yet the 2011 subduction zone rupture was devastating.

The Pacific Northwest, by contrast, is only In the 1980s, Cascadia learned about the danger posed by the subduction zone.

“Preparing for this is like trying to drain an Olympic-sized swimming pool with a teaspoon,” Ezelle said.

Science can help better prepare for the Big One

Highways, buildings, airports and other infrastructure in the Pacific Northwest need to be rebuilt to be “the best prepared we can be,” Ezelle said.

A more immediate and cost-effective strategy to save lives is to create a system that sends early warnings to phones; This is already true in many earthquakes, but it is not a guarantee.

The sooner the phone alert goes off, the more time people have to run and hide. The next frontier for this is laying cables containing seismic instruments along the seafloor, Tobin said. fault line. That’s what he’s trying to do at the Pacific Northwest Seismic Network.

Meanwhile, Tobin and other researchers are working to map the structure of the fault. Their latest work may have revealed some good news: The Cascadia subduction zone may rupture in pieces, or smaller earthquakes may occur, rather than a massive event all at once.

However, it remains unclear which scenario will actually occur (a Big One or multiple major scenarios).

“I don’t lose sleep over this,” said Tobin, who lives in Seattle beneath the snowy peaks of the Cascades.

The Cascadia subduction zone pushed these mountains upward about 10 million years ago and mountain range This makes the Pacific Northwest so fascinating.

“I would have to say that what creates earthquakes is part of what makes this a nice place to live,” he said.