Cascadia's Fault (21 page)

For Brian Atwater the next step was to ask two questions a lot of people were asking him: how big and how often? To find the answers he packed his kit and returned to the coast in the summer of 1987 to conduct a systematic survey by canoe of those three southern Washington estuaries: Copalis River, Grays Harbor, and Willapa Bay. He paddled miles and miles of shoreline and hiked through marsh, muck, and greasy river mud until persistence, and serendipity, paid off again.

In his initial reconnaissance at the Copalis River, he had walked in, venturing only a short distance from the road. “I missed the ghost forest,” he smiled, pointing across the lagoon toward the grove of weathered hulks bathed in sea mist and drifting fog. “It continues on upstream for another mile or two. It's spectacular all the way up.”

What made the dead trees important was the possibility that they could help pinpoint the year and season of the earthquake that presumably had killed them. The first scientist to try this tactic was David Yamaguchi, who had earned a PhD in forestry from the University of Washington and was working on a project for the USGS to use tree-ring dating as a way of figuring out when Mount St. Helens had erupted
prior
to 1980. He offered to help Atwater by trying this same technique to date the coastal earthquakes.

In May 1987 they took their first trip together to Willapa Bay. Atwater showed Yamaguchi the stumps of Sitka spruce, the main arboreal victims of great Cascadia ruptures. Yamaguchi chainsawed a few samples, but they didn't look very promising because tree-ring scientists usually prefer to sample from tree trunks—not stumps. Unfortunately, the spruce trunks had all but rotted away.

The great moment of good fortune came a few months later when they worked their way through the mist and saw for the first time the weather-beaten and moss-draped trunks of western red cedar—what would become known as the Ghost Forest of the Copalis River. “When
Dave and I first started working together, we didn't know that big forests of dead
cedar
trees existed,” Atwater told me. “Red cedar is more durable. The trunks are still here, standing dead three hundred years after they were killed.”

They figured similar trunks could probably be found along other tidal streams as well, and the more evidence, the better. Yamaguchi came up with the clever idea of placing ads in coastal newspapers, asking local residents if they knew about any more of these ancient beauties. And they did. Cards and letters arrived pointing them toward ghost forests near Grays Harbor, Willapa Bay, and along the Columbia River, a stretch of the Washington coast nearly sixty miles (100 km) long.

Did they all die during the same year and season? They should have if that entire segment of the coast had broken all at once in a single earthquake. Or did they instead die in different years at difference places as a result of a series of smaller earthquakes? Timing was everything.

Yamaguchi's first effort to establish a time of death for the spruce stumps had failed because, with all the rot, there were not enough rings left to count. But working with red cedars would be different. Step one of the ring-matching process involved finding a group of same-age trees that were at least as old as the ghost forest—and still alive—to establish a baseline growth pattern up to the current date. Wide rings that grow during good years with plenty of rain, for example, should be found in all the trees in the area. The same with narrow rings that grow in years of drought or fires or other kinds of trauma. The patterns should all match year by year, almost like fingerprints of the local climate.

Once this ring pattern was established, Yamaguchi would be able to work backward from the current year's growth ring and assign specific dates to individual rings in the past to determine in which year the ghost forest cedars died. Later in the summer of 1987 he and Atwater found the live trees they needed for comparison. At the time Weyerhaeuser was harvesting the fringes of a stand of old-growth red cedars that had witnessed—and survived—the great earthquake by inhabiting
a hillside above tides, on an island in the middle of Willapa Bay.

“It's a shame that these trees were being cut,” Yamaguchi commented. “They're beautiful trees. But we recognized that that was a place where we could gather modern reference samples.”

Each day after the loggers went home, Yamaguchi cut radial slices from the stumps they had left behind. Back at the lab, he drew diagrams with paper and pencil to confirm that they all shared a similar “bar code” of wide and narrow rings. Then he looked at the samples from the various ghost forests. “A number of them had more than two hundred rings in a series,” said Yamaguchi, “and it seemed like, at least theoretically, that would be enough for me to match against the living trees.” With a magnifying glass, a sharp pencil poised over his lab notebook, and an apparently infinite supply of patience, he began counting and cross-matching the rings of dead cedars against the baseline of cedars from the recent clearcut.

“When we started coming up with dates,” he recalled, “a few of the trees had rings up until the early 1690s.” The most precise date he could be sure of was 1691, meaning the trees had lived at least until then—maybe longer. It was impossible to nail the precise year of death because even the durable old cedars had taken a beating after three centuries of harsh coastal storms, bugs, fire, and rot. The outer bark and final ring of growth were simply not there any more. “The earthquake had happened sometime shortly after 1691,” Yamaguchi figured, “but I didn't know how many years afterward.”

Atwater and others at the University of Washington managed to narrow the timeline a bit more. He returned to the old quake-killed spruce stumps on the Copalis River and at Willapa Bay, where he chainsawed some samples that—unlike the cedar—still had intact bark. At the university, a team of radiocarbon analysts then used the spruce slices to limit the time of death to some time between 1680 and 1720—with a high degree of accuracy. Not an exact date, but at least it was progress.

In October 1987 Gary Carver, Bud Burke, and several of the graduate students at Humboldt State University were putting the final touches on a paper they intended to release in Phoenix at the annual meeting of the Geological Society of America. Their research on the tectonics of northwest California was finally ready for publication. Nothing splashy was planned, just another incremental step along the road to resolution of the Cascadia Subduction Zone mystery.

Bill Israel, a local journalist in Eureka, however, had been paying close attention to the news of this emerging Humboldt County seismic threat and recognized the implications of what the HSU team had found. He knew about Carver and Burke, he had read Heaton and Hartzell's comparison of Cascadia to Chile and Alaska, and he was aware of Brian Atwater's sunken coastline data. In the weeks leading up to the big convention in Phoenix, Israel had been hanging around the geology department at Humboldt State while the Carver and Burke paper was being polished.

Ever since the Ferndale earthquake in June 1975, when cracks had appeared in the concrete roadway leading up to the nuclear power station, Israel had kept tabs on the seismic risk analysis that PG&E was conducting. He knew about the Little Salmon fault and had learned of Gary Carver's growing list of other active fractures. When Tom Collins of the U.S. Forest Service recognized the distinctive rhombohedral fracture pattern in the sandpit across the road from the reactor and filed a report with the Nuclear Regulatory Commission, Bill Israel knew he was on to an important story.

He was also aware that Carver and Burke could not release their results to the media until the paper had been peer reviewed and published or presented formally at a gathering like the GSA meeting in Phoenix. So Israel collected bits and pieces of information, dug up background material about Heaton and Hartzell, Atwater, and others,
then bided his time, tacitly agreeing to embargo his story until the morning of the big convention when it would all become official.

“Somehow he got the idea we were predicting a giant magnitude 9 earthquake for Cascadia,” Carver told me. If you read the fine print of the document that was released in Phoenix that morning, neither Carver nor Burke said anything about a monster shockwave. But on Wednesday, October 28, 1987, the
Sacramento Bee
carried Bill Israel's story under a headline that proclaimed, “Giant Northwest quake feared.” The subhead made it even more ominous: “Researchers say 9.5 temblor possible.”

The opening sentence told a story of paradigm shift, another confirmation of the heretical new science: “New geological findings being released today support a growing body of scientific evidence that Northern California and much of the Pacific Northwest may erupt in a giant earthquake, potentially endangering thousands of lives and hundreds of critical structures.” The specifics of what Carver and Burke had found were buried seven paragraphs below and on the next page: “According to Carver and Burke, evidence from the Little Salmon fault suggests that the Cascadia subduction zone comes on land at Cape Mendocino, and that earthquakes of 8.5 or greater have occurred on the fault, perhaps over very large areas.”

It didn't take long for the
Bee
story to hit the wire services. Before the morning's coffee was cold, it had become a national news item. When Carver and Burke walked in to the convention hall in Phoenix they didn't see the ton of bricks that was about to land on their heads. “I was met by GSA officials and hustled off for interviews with the national press,” Carver recalled. “I had no idea what was happening. Bud and I had said nothing about magnitude 9 earthquakes in our talks or abstracts and knew nothing of Israel's article.”

Carver was not amused. “The meeting officials put a beeper on me so they could track me down,” he said. Through the blur of the next several hours he did “a bunch of interviews” trying to explain the giant
temblor story and trying even harder to dispel “the erroneous prediction” that Bill Israel had reported. “It was a trying day,” complained Carver. “When I got up to the podium that afternoon to give my talk, my beeper went off. The lecture room was standing room only and there were cameras and lights everywhere. I ignored the beep and got through the talk okay, but my nerves were shattered.”

Was the prediction erroneous? Or simply unattributed? A closer reading of the
Bee
story shows that the magnitude 9 line had come from Heaton and Hartzell's paper published back in April. The headline did not specify exactly who “feared” the giant shock, nor which of several groups of researchers mentioned in the story thought a 9.5 temblor was possible. Headlines seldom do. The new data from Carver and Burke were nowhere near as spectacular or unsettling as Heaton and Hartzell's cautionary tale, so the
Bee
's headline writer simply pulled zingers from the old story to sell a less dramatic new one.

Israel had been hanging around the geology department at HSU long enough to collect the personal quotes he needed to show where Carver and Burke were coming from. “The potential power represented by the magnitude of such earthquakes, Carver said, is ‘awesome, incomprehensible,'” Israel wrote. He quoted Bud Burke as saying, “We're living in a major earthquake zone . . . [The fault] is going to go in the next few generations—and it's going to be big. I don't think there's any question about it.”

Israel remembers it well. “I may have gotten them in a little trouble, but I don't think they felt badly about what happened at all. In fact, I think it helped propel them,” he said. “Gary had done a lot of work in Alaska himself, after the great Alaska earthquake. It was clear at the time that what he was seeing in Alaska was related to what was going on here. So it was a very good time to be a geologist of the new faith. And these guys were all a part of that wave.”

Looking back on it today, even Gary Carver sees some irony in the episode at Phoenix. “Interestingly, years later and based on the work
of a number of researchers, evidence for great subduction earthquakes has become widely accepted,” he told me in an email. Despite the scary headline, Bill Israel's story turned out to be accurate. Scientific opinion eventually caught up with Carver and Burke—even though they never really needed vindication. They had convinced Bill Israel that Cascadia's fault was capable of monster quakes, and Israel did what he had to do as a journalist to relay that dismal news to the rest of the world.

Once scientists had run through all the alternative explanations, eliminating the wrong answers and convincing themselves the new geology was right, then like it or not the next job had to be getting the word out. After OSU's Bob Yeats himself became “a convert,” he groaned about how difficult it was to get his wife, his neighbors, and state legislators in Oregon to take the coming quake seriously.