The next giant quake: It’s coming and here’s how
The compelling story of our last megaquake and how scientists are piecing together a picture of the future destruction: an excerpt from “Full Rip 9.0: The Next Big Earthquake in the Pacific Northwest” by Seattle Times science reporter Sandi Doughton (Sasquatch Books, $23.95).
Special to The Seattle Times
The following is an excerpt from “Full Rip 9.0: The Next Big Earthquake in the Pacific Northwest” by Seattle Times science reporter Sandi Doughton (Sasquatch Books, $23.95).
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Stories passed down from that night don’t tell us if dogs howled a warning. Huddled together in the cold, the animals might have sensed the first faint vibrations while the people still slept.
A quarter moon hung in the sky.
Far offshore, where only the boldest whalers paddled their canoes, a 700-mile-long gash on the ocean floor was shifting. Masses of rock thrust past each other, grinding and buckling and jerking as if the planet were being torn apart.
People jolted awake in their longhouses. The motion pounded out a staccato rhythm, like a woodpecker hammering a tree. Cedar planks rattled and timbers groaned. In those first moments, it might have seemed as if a gale were sweeping in off the Pacific Ocean. But how could the wind rock the ground? Children cried out in fear. Men and women stumbled toward doorways.
The ground began to roll like the sea. People dropped to their hands and knees, felled by shaking so intense cedar-bark baskets flew into the air. Ancient spruce trees whipped back and forth like saplings, raining branches onto the forest floor. The people lucky enough to make it outside clung in darkness to a world that seemed intent on casting them off.
As the seam in the seafloor continued to rip, the shaking swept along the western edge of North America. Under its thick blanket of mud, the margin of a great geologic plate shuddered and slid westward, pulling the continent with it. Shock waves raced out in all directions, traveling miles in seconds and rattling the shores of the inland sea many coast-dwellers had heard of, and some had even visited. The people who live there today call it Puget Sound.
ONE MINUTE PASSED.
Hillsides where condominiums now command million-dollar views trembled and sloughed off cascades of mud and stones. Deer and elk stampeded blindly but couldn’t escape the unearthly shaking. Nor could the people. From the Haida in the far north, to the Quileute on the Washington coast and the Yurok of California’s redwood forests, the tribes of the Pacific Northwest felt the earth reshaping itself beneath their feet.
Carved posts that had supported plank buildings for generations crashed to the ground. It was January, and the people were gathered in lowland camps for the winter. The river mouths, where many longhouses clustered, were the first to turn to jelly and spout geysers of watery sand. At the confluence where Portland would later spring up, sandbars vibrated into a slurry. Fountains spurted from spruce swamps along the Columbia River. The tideflats of the Duwamish River, today the busy port of Seattle, trembled and split. In the night, no one saw the undulations. Only later would people notice strange patterns left behind in the sand and silt.
Forested slopes gave way, rushing downhill in a tumult. River valleys and shorelines quivered and dropped by several feet. Stands of cedar that had sprouted centuries ago were suddenly below sea level. Some of the gray-haired elders had felt the earth shake before; this time they wondered if it would ever stop.
The year was 1700.
When earthquakes strike urban areas, they give off a dull roar like a jet passing overhead. The din rises from thousands of structures vibrating and grating against each other. What would the sound have been like centuries ago, when there was just the thrashing of forests and the wrenching of miles-thick chunks of crust?
The only signs of humanity were scattered native settlements. Imagine the scene today. What highway would remain passable after being tossed like a ship on the high seas? How many bridges and office towers could twist for four minutes and still stand? Pipelines that carry water, gasoline and oil to fuel a modern economy run through the same valleys that dissolved under the shaking so long ago. Power poles march over slopes that were scarred by landslides and littered with fallen trees.
Like a storm with its strength spent, the maelstrom in the earth subsided. The edge of the underwater plate ground to a halt, perhaps 50 feet from where it started. Along 700 miles of wild coastline, tribal communities that had never encountered each other rode out the final throes in tandem. In the stillness that followed, survivors must have felt as if they had slipped the clutches of an angry god. They couldn’t have known the most awful blow was yet to come.
Triggered by the upheaval on the ocean floor, swells were hurtling toward the coast faster than any fish could swim. Would the sliver of moon have cast enough light to reveal the sea pulling back? Surely people heard the thunder as the surge neared shore and gathered height.
The ocean stampeded across the land like a tide gone mad. No longhouse could stand up to the rush. Beaches where hundreds of thousands of tourists now fly kites and race three-wheelers on sunny days were swallowed by waves no man or beast could outrun. Uprooted trees became battering rams. Caught up in the icy water, people flailed desperately for anything to grab onto, anything to keep them afloat. Entire villages were swept away in a matter of moments.
THE EARTHQUAKE that lashed the Pacific Northwest in 1700 ranks among the mightiest the Earth can yield. Scientists today call it a megaquake — a magnitude 9 monster that ripped the full length of the offshore fault where seafloor and continent collide, and unleashed a killer tsunami. Only a few seismic disasters in modern times have approached that level of fury.
No one who saw the videos from the 2004 Indian Ocean megaquake and tsunami will ever forget the wall of water that pulverized cities and muscled through resorts as if they were made of cardboard. More than 200,000 people died. The force of the fault rupture made the Earth wobble on its axis.
In March 2011, an offshore fault ripped loose off Japan. The magnitude 9 quake shoved the island of Honshu eight feet to the east and triggered a tsunami that reached the closest shores in 20 minutes. A nation whose leaders thought they were prepared for the worst watched in horror as waves poured over sea walls and swept nearly 20,000 people to their deaths. Nuclear reactors crippled by the flood melted down and spewed enough radiation to turn the surrounding countryside into a no man’s land.
For Northwesterners, the images from Japan of doomed men and women running from the waves and tall buildings engulfed by water resonated in a visceral way. Even the world’s most earthquake-ready nation was no match for the kind of blow that had struck the Pacific Northwest more than three centuries ago — and which geologists now know will strike again someday. When it does, it will roil a human landscape that has undergone a tectonic shift of its own. The region called Cascadia is now home to more than 15 million people and several of North America’s most vibrant cities, businesses and ports.
“The ‘Big One’ in the Pacific Northwest has the potential to be the most costly and destructive disaster in the history of the United States, both in terms of loss of life and economic damage,” said James Lee Witt, former director of the Federal Emergency Management Agency (FEMA). “The long-term economic impact could alter our entire economy.”
Analyses from Oregon put that state’s possible death toll at 5,000 or more.
Rough estimates of economic losses in Oregon and Washington approach $80 billion, without factoring in damage from Northern California and British Columbia.
But the realization that the Cascadia region is vulnerable to the world’s most formidable earthquakes and tsunamis was slow in coming.
When the 1700 megaquake struck, the Pacific Northwest didn’t exist in the eyes of the world. Most maps of North America showed a void above California. England’s colonies were thriving on the continent’s eastern shore, but explorers didn’t begin to chart the coastlines of the Northwest with their snow-capped peaks and impenetrable forests until the end of the century. It was the mid-1800s before European and American settlers began arriving in large numbers.
By then, more than seven generations had passed since 1700. Some of the region’s indigenous people retained their collective memories of the cataclysm, but an onslaught of outsiders drowned out the native voices. The story of a night when earth and sea convulsed was lost to history.
If the newcomers paused to consider earthquakes, as they must have after San Francisco was reduced to a smoldering wreck in 1906, it was to congratulate themselves for living in a more solid place than California. In the 1920s, a geology professor named Collier Cobb surveyed the Puget Sound area and pronounced it earthquake-proof. “Los Angeles may shimmy with earthquakes and San Francisco may get another one,” he said, “but Seattle, set on the deepest glacial drift yet discovered, has a shock absorber which makes the city immune for all time.” The Chamber of Commerce & Commercial Club liked the quote so much they featured it in national newspaper ads.
It wasn’t until the mid-1980s that a young scientist digging in marshes along the Washington coast uncovered the first solid evidence of upheaval in the past. The rediscovery of the 1700 quake and tsunami is one of geology’s most remarkable detective stories. The finding ignited a revolution in earth science that’s still under way, still yielding insights into the forces responsible for both the region’s breathtaking beauty and its seismic perils. Once considered a backwater, the Pacific Northwest has been the epicenter of some of the world’s most exciting seismological research for nearly 30 years.
Piece by piece, scientists have re-created a history fraught with mayhem. If there’s one thing geologists grasp more fully than most people, it’s that what happened before will happen again. “People look upon the natural world as if all motions of the past had set the stage for us and were now frozen,” said geologist Eldridge Moores, in John McPhee’s “Annals of the Former World.” “To imagine that turmoil is in the past and somehow we are now in a more stable time seems to be a psychological need ... (But) the time we’re in is just as active as the past. The time between events is long only with respect to a human lifetime.”
Scientists now understand that the Northwest is even more seismologically complex than California, subject to three distinct types of earthquakes: deep, shallow and 1700s-style giants. California may rock more often, but it can’t rock as hard or in so many ways. The 1700 megaquake was 60 times as powerful as the quake that destroyed San Francisco.
Despite its outsized risks, the Pacific Northwest lags in its ability to cope with a restless Earth. Californians have had nearly two centuries to come to terms with the shaky ground they inhabit. In Japan people have been adapting to life with earthquakes for more than a thousand years. Northwesterners are still getting used to their region’s status as a seismic hot spot. For many, the discoveries of the past few decades have been nothing but bad news.
But the work of a generation of geoscientists has given the region the gift of foresight. It’s better to know what’s coming than to be caught off guard. Geologists may never be able to predict earthquakes, but they have been able to map out the Northwest’s seismic destiny in a level of detail that hasn’t been matched in many other parts of the world. Without having suffered through a great earthquake in modern times, the Pacific Northwest has been granted the chance to get ready before the next one strikes.
The new insights began to dawn in the 1960s, when geologists developed a comprehensive theory that for the first time made sense of why and where earthquakes occur. By the early 1970s, scientists strongly suspected the existence of an offshore fault — the fault that turned out to be responsible for the 1700 quake. But then they made the mistake of shrugging it off.