There was exasperation in his voice. Goldfinger was visiting Japan’s Tohoku University on March 11, 2011, and the experience made an activist of him. Watching the world’s most prepared nation brought to its knees by a giant earthquake and tsunami, he couldn’t help but imagine what’s in store for the Pacific Northwest.
Most scientists prefer to lay out their data and let the rest of society decide whether—or how—to act on the information. They couch their public statements in careful terms. Goldfinger doesn’t do that anymore: “This is not a good time to be wishy-washy,” he said. He’s been pushing the USGS to boost the earthquake hazard rating in Oregon and Northern California, where his research suggests more frequent quakes. He’s been urging parents to agitate for safer schools.
“Japan really changed my sense of urgency about getting things done here. We need to stop talking about this stuff and take action.”
CHAPTER 5:
SEATTLE’S FAULT
REVELATIONS ABOUT THE CASCADIA SUBDUCTION ZONE unnerved Northwesterners who grew up believing the worst thing that could happen to them, seismically speaking, was a midsize rattle like the ones that struck in 1949 and 1965. It took some getting used to, this notion that Washington, Oregon, and British Columbia could be slammed by the world’s most powerful quakes and tsunamis.
But even before the new reality sank in, geologists were about to ratchet up the region’s anxiety level again. A blitz of scientific sleuthing in the early 1990s found that the region is vulnerable to a third type of quake which, for the Northwest’s biggest city, could be the most destructive of all.
The story of what is now called the Seattle Fault began in the 1960s with a refugee from behind the Iron Curtain and a bunch of high school students. Decades later, scientists followed a trail of clues from the Olympic Mountains to a sewage plant on Puget Sound and an eerie, underwater forest in Lake Washington. A local businessman who helped with the research wound up in jail. Then in 1995, the once-obscure fault offered a tiny taste of what’s to come with a magnitude 5 earthquake that shook the ground from Oregon to the Canadian border.
Through all the saga’s twists and turns, Zdenko Frankenburger Daneš watched with a father’s interest. The fault was his baby, after all. But being the first to uncover evidence of its existence was for Daneš just the latest chapter in a life filled with adventure. As a young man during World War II he sabotaged telephone lines and derailed trains to foil Nazi occupiers in his native Czechoslovakia. When the Soviets took control of the country, they jailed and executed several of Daneš’s professors and fellow students at the University of Prague. He escaped to West Germany on a bicycle, careening down a mountain path with border guards close on his heels. Daneš immigrated to America and worked for the oil industry. By 1964 he was teaching physics at the University of Puget Sound (UPS) in Tacoma.
That summer Daneš volunteered for a program to give promising high school students a taste of scientific research. He had recently convinced university administrators to spend $3,600—enough to buy a new Chevy—on a secondhand instrument called a gravity meter. Daneš was eager to put the costly gadget to work.
Shaped like an oversized thermos, the meter contained a weight suspended at the end of a spring. It was designed to detect minuscule variations in gravity’s tug at different locations. Since dense rocks like basalt exert a stronger pull than more porous rocks like sandstone, geologists were quick to seize on the technique to map formations below the surface. Daneš suspected that something interesting lay beneath the spectacular topography of his new home. “The landscape just called out for it,” he recalled. So the pipe-smoking professor and nine teenage boys embarked on the first gravity survey of the Puget Sound region.
UPS alumni remember Daneš as a terrific teacher and a terrifying presence in the lecture hall. He always wore suits and never addressed students by their first names. But that summer Daneš let his crew-cut hair down. “He piled us into his old car, and he would drive around with the USGS quadrangle map on the steering wheel,” recalled Wayne Gilham. Now a Tacoma yacht broker, Gilham was sixteen that summer and a self-described science nerd.
The group meandered back roads and hiked to hilltops in search of survey markers where they would set up the gravity meter—very carefully. “Dr. Daneš let us know how expensive it was,” Gilham said. The teenager hammered together a plywood runabout and used it to motor around Puget Sound with the other boys, taking readings along the shore. Back at the UPS campus, the students crunched the numbers by hand and slide rule.
In 2011, at the age of ninety-one, Daneš amazement over what he and the teenagers found hadn’t dimmed. “My God. It was exciting,” he said. “We saw it almost immediately.”
“It” was an abrupt change in gravity measurements along a line that slices from Hood Canal through south Seattle. North of the line are lighter, sedimentary rocks. To the south, the rocks are dense and heavy. A 150-pound person loses about two-tenths of an ounce traveling north from Sea-Tac Airport to the University of Washington because of the difference in gravity pull.
The gravity gradient is one of the sharpest ever detected in the United States. To Daneš it could mean only one thing: a geologic fault. Motion on the fault—essentially past earthquakes—would explain the dramatic offset in rock layers beneath much of Washington’s urban core.
Daneš wrote up the results, crediting all the teens as coauthors. The Journal of Geophysical Research published the paper on November 15, 1965. Gilham still keeps the volume in his bookshelf, as does Daneš, who went on to collect more than eleven thousand gravity measurements across the state. But the findings didn’t stir up much interest at the time. The loudest reaction came from real estate agents. Any talk of earthquakes was bad for property values, and they gave the professor an earful for scaremongering.
The Realtors were right to be worried. As in the housing market, location is key to earthquake damage. The quakes that hit Puget Sound in 2001, 1965, and 1949 originated more than thirty miles underground, deep inside the subducting Juan de Fuca Plate. The intervening miles of rock act as a buffer to dampen shaking at the surface.
There’s no shock absorber when a quake strikes right under your feet. What Daneš was suggesting was a fault that passed a few scant miles below the homes and high-rises of Seattle. A magnitude 6.8 quake on such a shallow fault could rock parts of the city nearly four times as hard as the 2001 Nisqually quake of the same size. California’s 1994 Northridge quake, the costliest in U.S. history, came from a shallow fault. So did Haiti’s devastating 2010 quake and the one in Kobe that killed nearly six thousand people and leveled one of Japan’s busiest ports in 1995.
Daneš’s report was tantalizing, but far from conclusive. The fault was probably real, but was it dangerous? Or had it stopped moving long before mammoths roamed the Northwest? Oil companies were intrigued enough to check it out, because faults can create pockets where petroleum collects. Mobil, Chevron, and others sailed Puget Sound in the early 1970s surveying the seafloor. But the companies kept the data to themselves. Over the next decade, USGS mappers noted several features that added to the evidence for the fault’s existence. But it wasn’t until the late 1980s that Robert Bucknam, of the USGS’s Denver office, decided to follow Daneš’s footsteps in a serious way.
Even as he flew into Seattle, Bucknam could see it was going to be tough. The landscape wasn’t like the Utah desert where he’d been working for the past several years. “There, you could see everything, almost as if the ground was stripped bare,” he recalled. In Washington, the glaciers that covered the Puget lowlands as recently as sixteen thousand years ago scoured away most signs of past earthquakes. Lush vegetation hid the rest. Working in an urban area that was home to nearly three million people would also be a challenge.
Like Atwater on the Pacific coast, Bucknam focused on shorelines to see if they had dropped or had been shoved up in the past. One of his best leads was on Bainbridge Island, the low-slung land mass Seattleites see wh
en they look west. The USGS mappers had found clam beds there sitting more than a dozen feet above the modern water level. Bucknam decided to explore the island for other signs that it had been jolted in the past.
He soon found what he was looking for at the island’s southeastern tip. British Navy Captain George Vancouver dropped anchor there during his 1792 explorations, intrigued by the treeless bench that wrapped around the point and was so unlike the steep bluffs and closed-in forests that dominated most of Puget Sound’s shores. He named the spot Restoration Point, in honor of England’s return to monarchy after a fit of republicanism. A golf course now occupies much of the point, and some of the priciest homes north of Beverly Hills gaze out on Puget Sound from a gated community. But what Bucknam saw in the serene landscape made him suspect a history of violence.
The bench that caught Vancouver’s eye is what geologists call a marine terrace: an ancient waterfront that rose out of the sea. On its surface Bucknam found beach gravel and fossil clams burrowed into the rock. The broad bench is backed by a cliff that once sat at the water’s edge and still shows the marks of lapping waves. “It was quite clear it had been uplifted,” Bucknam recalled. But landforms can rise for many reasons. He couldn’t rule out the possibility that the point had simply rebounded when the immense weight of Ice Age glaciers melted away.
Tall and quiet, Bucknam worked methodically. He paced every square meter of the bench, looking for the type of erosion that would have eaten away at the sandstone if it had risen slowly over a period of centuries. He found none. The bench must have popped out of the water in a matter of moments. Bucknam measured the uplift at twenty-three feet.
The USGS scientist had found the first physical evidence that Daneš’s fault was not only real but active. It had produced at least one quake, and a big one at that. A similar upheaval today would devastate the cities and suburbs that had sprung up across the region since Vancouver dropped anchor two centuries ago. But how widespread were the quake’s effects? And when did it hit?
From where Bucknam was working on the tip of Restoration Point, he could look across Puget Sound to Alki Point in the West Seattle neighborhood. It was on Alki that the city’s first white settlers established their foothold. Bucknam saw that Alki was also ringed by a broad, flat bench. For centuries native people found a dry perch there above the tides, a feature that must have been attractive to the white pioneers, too.
Bucknam shifted his focus from Bainbridge Island to the mainland. His assistant for much of the work was Brian Sherrod, a stocky graduate student from Virginia who would eventually land a job with the USGS and delve even more deeply into the Seattle Fault’s past than his mentor. More than a decade after he and Bucknam first studied the area, Alki remains Sherrod’s favorite place to bring visitors and students who want to see what the Seattle Fault is capable of. “To me, Alki really brings it home,” Sherrod said. “It’s right in the middle of the city.”
On a spring morning in 2012, after a line of squalls blew through, Sherrod drove past Tully’s, Pegasus Pizza, and the condo complexes on Alki Beach that boast the city’s best views of the Seattle skyline. He rounded the point, with its century-old lighthouse, and turned onto Beach Drive Southwest.
The road skirts the beach for miles. It’s such an urban scene—sidewalks, streetlights, houses, and apartments—that it’s hard to read anything menacing into the fact that the pavement rests atop a bench several feet higher than the beach. The bench is crowded with homes and apartment buildings, stacked four deep at its widest spots. Sherrod pulled his truck to the side of the road and got out. “We’re basically standing on the old beach,” he explained. Just as at Restoration Point, he and Bucknam found that Alki Point had been lifted abruptly in the past.
Well back from the road, Sherrod pointed out a steep cliff cloaked in blackberry and ivy and topped with houses. On a rainy Saturday nearly ten years before, he and Bucknam hopped the fence of an adjacent city pump station and dug holes at the bottom of the cliff. What they found a full city block from the waterline was beach gravel—proof that the cliff once stood at the water’s edge. The earthquake lifted the land here more than twenty feet. “Just picture it,” Sherrod said, looking around at the densely-packed neighborhood.
When Sherrod and Bucknam cast a wider net for the earthquake’s footprint, they found evidence of uplift twenty miles east on Hood Canal and nearly fifty miles south near Olympia. The fault geometry really clicked for Bucknam when he poked around in a small marsh back where he started, on Bainbridge Island. The bog was only three miles from Restoration Point, but it lay on the other side of the gravity line Daneš and his students had mapped across Puget Sound. Bucknam discovered that the marsh hadn’t been lifted at all. In fact, it had dropped slightly.
The pieces fell into place. When the Seattle Fault slipped, shorelines to the south, including Restoration Point and Alki, were raised. Shorelines and marshes to the north either stayed put or dropped. Based on the size of the uplift he measured around Puget Sound, Bucknam figured the Seattle Fault quake was at least magnitude 7, and quite possibly bigger.
He was less successful pinning down a date. A botanist and diatom expert carbon-dated marine fossils and organic material from the sunken bog on Bainbridge Island. But the best they could say was that the quake struck sometime between 500 and 1,700 years ago.
News of Bucknam’s early findings spread quickly in the late 1980s through a community of scientists already energized by the Cascadia discoveries. Through coincidence, serendipity, and design, more than a dozen researchers joined forces in a kind of scientific SWAT team to figure out when the quake hit and flesh out its impact. Their findings showed that the most recent spasm on the Seattle Fault did a lot more than lift beaches. It also sent old-growth forests plunging into a lake, set off avalanches of rock that plugged valley bottoms, and hurled a tsunami across the shores of Puget Sound. Collectively, the threads of evidence added up to one of the most comprehensive cases ever made to prove an ancient earthquake.
Brian Atwater got drawn onto the SWAT team in 1991. He was mostly working on the Pacific Coast, but heard about a billion-dollar construction project under way on Puget Sound. New federal rules were forcing Seattle to upgrade its aging sewage-treatment plant at West Point, near the city’s Magnolia neighborhood. Engineers were installing a new outfall pipe big enough to drive a Humvee through. The trench they dug would open a once-in-a-lifetime window into the geologic past.
Atwater convinced project managers to call him when crews finished excavating each new section of trench. He would then rush down to examine the soil layers before pipe was laid and the hole filled in.
The angled walls of the trench loomed three stories above Atwater’s head, and held thousands of years of history. The site’s long occupation by Native Americans was recorded in a purple midden of mussel shells, animal bone, and fire-blackened rock. Layers of mud marked ancient landslides that had sloughed off the surrounding cliffs and spread across the salt marsh. The wetlands were trampled during World War II, when the army used the area to practice amphibious landings. In the 1960s the marsh was buried under ten feet of sand for construction of the original treatment plant.
Between the peak of the native occupation and the modern era, Atwater discovered a layer unlike all the others. It was a sheet of sand several inches thick, like those he found in the banks of the Niawiakum River. A huge wave had washed over West Point at the same time the land dropped by several feet. Entombed in the sand were bulrush stems, still standing upright. He unearthed barnacle-encrusted sticks so well preserved they snapped in two with an audible crack. “It was just spectacular,” Atwater recalled. A graduate student working with him found a similar buried sand sheet in a pasture at the tip of Whidbey Island, twenty miles north of Seattle.
Radiocarbon analysis at both sites yielded a date between 900 and 1,300 years ago. That was close enough to Bucknam’s time frame to suggest more than coincidence. It also made sense that big waves would have
rushed up the Sound. If a quake thrust beaches twenty feet in the air, it would have done the same to a big swath of Puget Sound’s bottom. Just as in the ocean, displaced water can create a tsunami in inland waterways.
A team of geologists working in the Olympic Mountains reeled in radiocarbon dates in the same ballpark when they sampled snags in lakes likely formed when the earthquake shook loose avalanches of rock and dammed streams. The rising water killed the trees.
Another group extracted mud cores from the bottom of Lake Washington that showed a succession of underwater landslides. The biggest corresponded in time with the Puget Sound tsunami and the Olympic Mountain avalanches. In fact, so many radiocarbon dates were falling into the same time window that scientists joked they didn’t even need to bother with the tests.
But the window was still too wide. As with Cascadia’s most recent quake, drowned trees would prove to be the most precise chronometers.
People who live around Lake Washington have long known about the mysterious forests that rise from the lake bottom. The long-dead trunks don’t poke up above the water, but they extend close enough to the surface to have snagged miles of fishing line and eaten countless anchors. When construction of the Ballard Locks lowered the lake level in 1916, several boats ran afoul of the trees. The U.S. Army Corps of Engineers used steel draglines to wrench nearly two hundred Douglas firs out of the navigation lanes. The largest was 9 feet in diameter. The longest measured 121.5 feet. Many were impossible to budge, so the engineers used dynamite to blast off their tops.
A diver who explored one of the forests in 1957 found himself “engulfed in a densely forested bottom” 90 feet down. Many trees were standing upright, apparently having ridden a landslide into the water. Using a crane, workers pulled up one intact fir for scientists to sample. Radiocarbon dating was in its infancy, but the results suggested the tree died between 800 and 1,400 years ago.
Full-Rip 9.0: The Next Big Earthquake in the Pacific Northwest Page 9
