Just over one year ago, a magnitude-9 earthquake hit the Tohoku region of northeastern Japan, triggering one of the most destructive tsunamis in a thousand years. The Japanese—the most earthquake-prepared, seismically savvy people on the planet—were caught off-guard by the Tohoku quake’s savage power. Over 15,000 people died.
Now scientists are calling attention to a dangerous area on the opposite side of the Ring of Fire, the Cascadia Subduction Zone, a fault that runs parallel to the Pacific coast of North America, from northern California to Vancouver Island. This tectonic time bomb is alarmingly similar to Tohoku, capable of generating a megathrust earthquake at or above magnitude 9, and about as close to Portland, Seattle, and Vancouver as the Tohoku fault is to Japan’s coast. Decades of geological sleuthing recently established that although it appears quiet, this fault has ripped open again and again, sending vast earthquakes throughout the Pacific Northwest and tsunamis that reach across the Pacific.
What happened in Japan will probably happen in North America. The big question is when.
On a foggy spring morning just before sunrise, 27 miles northwest of Cape Mendocino, California, a pimple of rock roughly a dozen miles below the ocean floor finally reaches its breaking point. Two slabs of the Earth’s crust begin to slip and shudder and snap apart.
The first jolt of stress coming out of the rocks sends a shock wave hurtling into Northern California and southern Oregon like a thunderbolt. For a few stunned drivers on the back roads in the predawn gloom, the pulse of energy that tears through the ground looks dimly like a 20-mile wrinkle moving through a carpet of pastures and into thick stands of redwoods.
Telephone poles whip back and forth as if caught in a hurricane. Power lines rip loose in a shower of blue and yellow sparks, falling to the ground where they writhe like snakes, snapping and biting. Lights go out and the telephone system goes down.
Cornices fall, brick walls crack, plate glass shatters. Pavement buckles, cars and trucks veer into ditches and into each other. A bridge across the Eel River is jerked off its foundations, taking a busload of farm workers with it. With computers crashing and cell towers dropping offline, all of Humboldt and Del Norte Counties in California are instantly cut off from the outside world, so nobody beyond the immediate area knows how bad it is here or how widespread the damage.
At the U.S. Geological Survey (USGS) lab in Menlo Park, seismometers peg the quake at magnitude 8.1, and the tsunami detection centers in Alaska and Hawaii begin waking up the alarm system with standby alerts all around the Pacific Rim. Early morning commuters emerging from a BART station in San Francisco feel the ground sway beneath their feet and immediately hit the sidewalk in a variety of awkward crouches, a familiar fear chilling their guts.
Then another little rough spot on the bottom of the continent snaps off.
The fault unzips some more.
The outer edge of California snaps free like a steel spring in a juddering lurch—nine feet to the west. The continental shelf heaves upward, lifting a mountain of seawater.
The fault continues to rip all the way to Newport, Oregon, halfway up the state. The magnitude suddenly jumps to 8.6. A power surge blows a breaker somewhere east of town and feeds back through the system, throwing other breakers in a cascade that quickly crashes the entire grid in Oregon, Washington, and parts of California, Idaho, and Nevada. A brownout begins in six more western states. The wire line phone systems crash in lockstep.
Then another fragment of rock deep underneath Newport shears away. The fault unzips the rest of the way to Vancouver Island. The quake now pins seismic needles at magnitude 9.2. High-rise towers in Portland, Seattle, Vancouver, and Victoria begin to undulate. The shock wave hammers through sandy soil, soft rock, and landfill like the deepest notes on a big string bass. The mushy ground sings harmony and tall buildings hum like so many tuning forks.
On I-5, the main north-south interstate highway, 37 bridges between Sacramento and Bellingham, Washington, collapse or are knocked off their pins. Five more go down between the Canada–United States border and downtown Vancouver. Nineteen railway bridges along the north-south coastal mainline of the Burlington Northern Santa Fe railway are wrecked as well. The runways of every major coastal airport from Northern California to Vancouver are buckled, cracked, and no longer flyable.
After 50 cycles of harmonic vibration—skyscrapers swaying rhythmically from side to side in giddy wobbles—dozens of tall buildings have shed most of their glass. In some downtown intersections the cascade of broken shards has piled up three feet deep.
Shock waves have been pummeling the Pacific Northwest for four minutes and thirty-five seconds now, and it still isn’t over. After 64 cycles, enough welds have cracked, enough concrete has spalled, enough shear walls have come unstuck that some towers begin to pancake. The same death spiral everyone saw in New York on 9/11 happens all over again. Smaller buildings, but more of them. Dozens of towers go down in the four northernmost of the affected cities.
In the five major urban areas along the fault, tens of thousands of people have been seriously injured. Hundreds, perhaps thousands, are dead. More than a third of the oncoming shift of police, firefighters, paramedics, nurses, and doctors do not show up for work. They are either stranded by collapsed buildings, bridges, and roadways, injured or dead themselves, or have decided to stick close to home to make sure their own families are OK before going to work. People who survive the collapses must do their own search and rescue for family members, friends, and neighbors still trapped in the rubble. Help will come eventually, but who knows when?
People in the United States and Canada, if they think at all about earthquake disasters, probably conjure up the San Andreas fault in the worst-case scenario. In California, as they wait for “the Big One,” people wonder which city the San Andreas will wreck next—San Francisco or Los Angeles? But if by the Big One they mean the earthquake that will wreak havoc over the widest geographic area, that could destroy the most critical infrastructure, that could send a train of tsunamis across the Pacific causing economic mayhem that would probably last a decade or more—then the seismic demon to blame could not possibly be the San Andreas. It would have to be Cascadia’s fault.
One year after Japan’s devastating Tohoku earthquake and tsunami, scientists are still trying to figure out how the world’s most organized and earthquake-ready nation could have been taken so much by surprise. They were hit by an earthquake roughly 25 times more powerful than experts thought possible in that part of the country. How could the forecast have been so wrong? The short answer is they didn’t look far enough back in geologic time to see that quakes and tsunamis just this big had indeed occurred there before. If they had prepared themselves for a much larger quake and wave, the outcome might have been entirely different.
Discover Magazine
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