Cascadia's Fault

by Jerry Thompson

  The San Andreas has and will again cause terrible, destructive earthquakes, probably sooner rather than later, but the offshore temblor from Cascadia will be on a much larger scale. The San Andreas will wreck a major urban area—perhaps San Francisco or Los Angeles—but probably not both at the same time. Cascadia’s fault will hammer an entire region of the planet, just as the Sumatra disaster did.

  I know it’s not scientific, but just for the sake of comparison, I fashioned a small ruler out of a piece of paper and held it up against a globe. I put a pencil mark midway up Vancouver Island and another at Eureka, California, creating a paper proxy for Cascadia’s fault. Then I moved it to the east coast of North America. An eight-hundred-mile (1,300 km) tectonic crack like this—if it started in New York—would run down through Philadelphia, Baltimore, and Washington to about Charleston, South Carolina. The same fracture, if it started in Detroit, would run past Niagara Falls, through Toronto and Montreal to roughly Quebec City. Or from London through Paris to Nice, France. Or from Lisbon across Portugal to Barcelona. Or from Berlin to Milan.

  There’s evidence to suggest that Cascadia’s fault would not act alone—that an earthquake along this subduction zone could transfer enough stress to trigger the San Andreas at the point where the two faults connect, near Cape Mendocino, about three hundred miles (480 km) north of San Francisco. Mud-core sampling of undersea landslides off the Pacific Northwest and California coasts has revealed a fairly close time correlation between ruptures on the two fault systems for many of the largest quakes in the past.

  It could happen like this: a magnitude 9 rupture on Cascadia causes an unprecedented natural disaster that affects the entire Pacific Rim. It also sends a strong jolt into the neighboring San Andreas system, which is already nearing its own failure along the Hayward fault in Oakland. Ten or twenty years later, while Americans and Canadians are still rebuilding from the recent Cascadia event, the San Andreas rips loose and California is back on its knees again.

  That’s not all. Cascadia will also slam the beaches of the west coast of North America as well as Alaska and Hawaii. A research plan prepared by NOAA—the National Oceanic and Atmospheric Administration—back in 1982 estimated that 900,000 people would be at risk from a fifty-foot (15 m) Cascadia tsunami striking the U.S. western seaboard.

  But that’s just the United States. Nobody has done a projected death toll for the other Pacific Rim nations that would be affected. Researchers have, however, made a convincing case that an earthquake on Cascadia’s fault in 1700 put a series of waves thirteen to sixteen feet (4–5 m) high—imagine water more than fifteen feet above the highest tides—onto the beaches of eastern Japan, causing widespread damage, injuries, and deaths. At this point one can only imagine what the same waves would do to the seaports and villages of modern-day Japan. To this scenario add Indonesia, Hong Kong, the Philippines, New Guinea, Australia, and New Zealand—all of which would be hit by Cascadia’s waves.

  And now we’ve learned that the effects could be even worse than previously imagined. The evidence from Sumatra, translated into numerical code and applied to updated computer models of Cascadia, confirms that some of the waves generated could be as high as seventy to ninety feet (20–30 m). Earlier computer simulations had put the maximum wave height at roughly fifty to sixty-five feet (15–20 m). Looking at footage of what a ninety-foot wall of water had done to one beach near Banda Aceh in 2004, an emergency manager from FEMA, the Federal Emergency Management Agency, shook his head and told a journalist from CNN that quite frankly no town on the western U.S. coast had any idea how to plan for or cope with that kind of wave.

  Canada’s situation will be considerably worse. Federal and provincial emergency planners in British Columbia are laughably underequipped and underfunded. Canada doesn’t even have a national guard to take over when local governments are quickly overwhelmed—as they surely will be when Cascadia rips loose.

  At NOAA’s laboratory in Seattle, chief oceanographer Eddie Bernard says the easiest way to put Cascadia’s fault into perspective is to “multiply the New Orleans disaster times four or five.” Imagine having five Hurricane Katrinas—hitting five different cities—on the same day. Other experts believe Cascadia’s next big temblor will be the largest peacetime disaster in North American history.

  As a journalist and documentary filmmaker I have covered the Cascadia earthquake story at least five times over the past twenty years and have talked to dozens of geologists, seismologists, civil engineers, and oceanographers. With each new evolution or refinement of earthquake and tsunami science, I have been stumped in the final scene by the same nagging question. Do I make things better or worse by warning people about an event that may not happen in their lifetimes? If I take the latest scientific evidence, show that a monumental disaster is probably overdue and issue a dire warning—what do I accomplish? The initial shock wears off quickly. After that, nothing much changes.

  All I’ve done in telling the tale is to make people more depressed than they already were. Folks who live around the Pacific Rim have heard this wake-up call many times before and disaster fatigue creates inertia. Because there are so many worrisome things to obsess about—global warming, terrorist attacks, killer plagues, and asteroid impacts, to name a few—disaster stories are losing their punch.

  Unfortunately Cascadia’s menace remains, whether those of us in the danger zone respond to it or not. What happened to Sumatra in 2004 will happen to North America, beyond any reasonable scientific doubt. A nearly identical earthquake will rattle the West Coast and a train of killer waves will tear across the Pacific.

  One might argue that because I know what’s going on, I have a moral obligation to spread the word even if I don’t know how to respond to it myself. A replay of the Indian Ocean disaster along the shores of the North Pacific is absolutely going to happen. And Bette and I will be in harm’s way when it does.

  We live on a bluff above the sea on the mainland coast of British Columbia, about two hours’ drive north of Vancouver. We have no idea how well our condo will withstand four minutes of intense shaking. Civil engineers generally agree that well-built wood-frame structures are flexible enough to ride out most earthquakes without collapsing, but Cascadia’s shockwaves will reverberate far longer than most quakes. We tell ourselves we’ll be okay, that the condo may be damaged but we’ll probably get out alive. How then do we cope with the aftermath?

  We’re two hours away from the nearest big city, Vancouver, which may be in much worse shape than our own coastal hamlet. Rescue squads, medical aid, and emergency supplies will go first to the areas of greatest need, where the greatest numbers of people are affected—and where television cameras will focus the world’s attention. To us this means help may be a long time coming to Sechelt, so we’re pretty much on our own.

  When they hear that I’m working on the Cascadia story yet again, friends and neighbors usually cringe. The first question everyone asks is when it’s going to happen. I tell them I don’t know, but some very smart people are trying to figure it out. Then they shrug. What can we do? It’s too overwhelming to think about.

  PART 1

  TREMORS AND RIPPLES

  CHAPTER 1

  Mexico City: Preview of Coming Events

  On the night of September 19, 1985, a jetliner packed with journalists, foreign rescue workers, and worried family members banked low across the flanks of Mexico City. The twinkling sprawl of suburbia gradually gave way to a black hole at the heart of the city. Only the twisting flames of unquenched fires and pockets of light powered by emergency generators penetrated the gloom. From window seats on final approach it was impossible to see the full extent of damage down below, but every person on that plane knew they were about to land in the haze of an ongoing nightmare.

  Even on the ground visibility was so limited the arriving passengers could not appreciate how bad things were that first night. Robb Douglas, a Canadian television news cameraman, went to work straight away using a
battery-powered lamp to shoot pictures of rescue teams digging through hunks of broken concrete and twisted steel. All he could capture in the small beam of light projected from his camera were close-cropped images of frenzied workers—their grim, sweat-streaked, exhausted faces. Dust and smoke and death.

  Early the next morning the scale of the disaster revealed itself. “When the sun came up you could see—holy shit! It looked like it had been bombed—like the city had been bombed,” Robb would tell me later. “All those buildings had just dissolved.” In little more than three minutes of horrific shaking, 10,000 people had died. Unofficial estimates would later push the death toll to 40,000 or more. Another 50,000 were injured and 250,000 were homeless.

  In the city proper, 3,124 buildings were severely damaged and 412 had collapsed. If you included the impact on outlying regions, more than 6,000 buildings had either been destroyed or so heavily damaged they would have to be demolished. With a population of eighteen million, the world’s second largest city was reeling from the blow and woefully unprepared for the aftermath.

  Those of us who did not see it first-hand, who did not stand like Robb on the brink, who did not smell the blood or hear the screams barely paid attention. If we didn’t know someone who lived there, it was one more disaster, far away and too gruesome to think about. But flash back several months to the summer of 1985 and consider the context.

  On June 23, a terrorist’s bomb blew Air India flight 182 from the sky off the Atlantic coast of Ireland, killing 329 passengers. On July 19, the Val di Stava dam in northern Italy collapsed, killing 268 people. On August 2, Delta Air Lines flight 191 crashed near Dallas, killing 137 people. Ten days later a Japan Airlines flight from Tokyo to Osaka crashed, killing 520, the deadliest single-aircraft accident in history. A crash on September 6 outside Milwaukee killed 31 more. Disasters had dominated the summer headlines with depressing regularity.

  On Thursday, September 19, the morning the earthquake wrecked Mexico City, I was working in New York on a Canadian Broadcasting Corporation television documentary about a handful of Russian soldiers who had defected in Afghanistan and escaped to the United States. By the time the first shockwave (magnitude 8 on the Richter scale) hit the Mexican capital at 7:19 a.m. local time, the CBC camera crew and I had already left our Manhattan hotel. The front page of the New York Times carried stories about an American hostage in Lebanon freed after sixteen months of captivity and a feature about police corruption in Philadelphia but nothing about Mexico City, of course, because the paper had gone to bed the night before.

  Off to a good start on the Soviet defector story, I worked my way through the first full day of Mexico’s tragedy without hearing a word about it. I was focused on “Russia’s Vietnam,” blissfully unaware of the mounting death toll in that smoky, flickering cauldron more than 1,800 miles (3,000 km) to the south and west. I did not know about heroic efforts underway to tunnel beneath the buckled walls and floors of a hospital to find survivors. I could not see the heartbreaking pictures my friend Robb was shooting at that very moment.

  Even had I heard a radio newscast as we rattled over potholes and lurched back into New York just before midnight, the Mexico City story probably would not have fazed me as much as it should have. I had never experienced a disaster like that myself, so I had no effective way to process the information, no visceral sense of what it was like to feel the earth heave or to see the known world come crashing down around me. My awareness of distant tragedies was limited to a mental montage of anonymous, grieving widows, orphaned children crying, broken men with vacant stares, collapsed buildings, and body bags.

  About a dozen years in television news and documentaries had sent me around the world more than once, but somehow I’d never been assigned to cover a natural disaster. An evolving cynic at the ripe old age of thirty-six, I had filed plenty of stories about human mayhem from places where the roads were mined and people tended to shoot at each other—places like Nicaragua and Honduras, Sri Lanka and the Punjab. But floods, typhoons, and earthquakes were terra incognita.

  For me these doomsday stories had an air of unreality about them. The numbing repetition of so much tragedy, packaged neatly into two-minute doses and delivered almost instantly by television news, blunted my reaction. Disaster shock tended to fade quickly.

  I was ignorant not just of the people struggling to survive that night in the Mexican capital but of the scientific significance of the earthquake itself. I would not learn until weeks later that the “event” (as geologists would refer to it) had come as a bit of a surprise. The offshore fault that ruptured had been quiet for perhaps two hundred years even though smaller earthquakes had occurred on either side of the rupture zone.

  The quiescence of the Michoacán segment, roughly 190 miles (300 km) southwest of Mexico City, had convinced some seismologists that this particular fragment of the earth’s crust was for reasons unknown a special case. Two tectonic plates were apparently sliding past each other smoothly. No stress, no worries.

  Was there some kind of subterranean lubrication that kept the plates from getting jammed up? No one knew. But for as long as humans had kept written records, this zone and a few others like it around the world had not generated large, destructive earthquakes. Therefore, this particular stretch of the Mexican coast was thought to be aseismic—not likely to produce major earthquakes.

  At sunset on Friday, September 20, Robb Douglas and his soundman Gunter Mende stood at the base of what might once have been a thirty-story apartment building but was now a twisted heap. Next to the destroyed building stood two more towers that looked to be part of the same complex. What caught Robb’s eye was the apparent randomness of the wreckage. It was obvious the other two had been badly damaged and could collapse at any moment, but they were still vertical. Why? His pictures raised questions that civil engineers would be forced to answer in the coming months.

  As Robb lined up his next shot, the ground started to shake violently beneath his feet. At 6:30 p.m., thirty-six hours after the initial shockwave, a magnitude 7.5 aftershock (some experts believe it was another, completely separate earthquake) instantly made a bad situation worse. People who’d counted themselves lucky, who’d thought they had survived the disaster, realized in a heartbeat that it wasn’t over yet. Hundreds ran screaming from homes and apartments in the congested neighborhood surrounding the three towers.

  They swarmed across sidewalks and into the streets. Some scrambled into cars and tried to make a getaway, racing toward a nearby freeway on-ramp. “I got shots of everybody running through the streets, trying to get in their cars to drive away,” said Robb, “but it was hopeless.” A torrent of humanity choked the only avenue of escape.

  The TV camera was locked on a tripod and the recording deck was connected by a thick black cable, so Robb and Gunter were shackled together. With nowhere to run, they hunkered down, two rocks in a river of terrified people. “It happened so quickly. It’s not like you have any warning.” The more Robb told me the more vividly the scene came back into focus for him. “We were so frightened, we couldn’t even move. I was just weak in the knees.” This from a guy who doesn’t get rattled by much.

  Sensing movement over his shoulder, Robb glanced up and saw in a darkening sky that the two remaining towers, thirty stories high, were bending from side to side like tall trees in a wind storm. “When we saw those other two buildings moving back and forth like that, swaying—and you know one had already collapsed—and we were right beside’em, we figured we were in the wrong place.” But Robb and Gunter were lucky that night. The towers did not fall. And they lived to tell the tale.

  Mexico had survived plenty of big earthquakes—forty-two of magnitude 7 or higher in the twentieth century—but nothing as big as the shockwave of September 19 had occurred there in all of recorded history. So geologists immediately started looking for ways to make sense of what had happened. An eerily similar offshore quake had rocked Alaska in 1964. Chile’s 1960 seafloor rupture, at magnitude 9
.5, was the largest earthquake ever recorded in the world. In both cases the faults that caused the quakes were impossible to examine, concealed beneath thousands of feet of seawater.

  Geologists who’d suggested the Michoacán segment of the Mexican seaboard was somehow a special case—an aseismic zone—were about to face a steep new learning curve. But they weren’t alone. Earth scientists around the world were undergoing a paradigm shift, a fundamental change in thinking about how the planet had formed, how mountains were built, and what makes huge earthquakes happen. For more than three decades, starting in the mid-1950s, much of the conventional wisdom of geology had been debated, updated, and revised by fresh data and new ideas.

  By the mid-1960s a new hypothesis called plate tectonics had emerged from the dust of an earlier and much ridiculed theory known as continental drift (more on this later). But in 1985, twenty years after tectonic papers began to appear in the science literature, the idea was still relatively new and more than a little controversial. Not everyone had come to terms yet with the concept of slabs of the earth’s crust, forty to sixty miles (70–100 km) thick, floating around on convection currents of superheated, semi-liquid rock, crashing and grinding against each other, creating jagged mountain ranges like the crumpled fenders of a car wreck, generating giant earthquakes in the process.

  Even basic things like the textbook definition of a fault—a rupture in rock along which movement has taken place—had become vastly more complex in light of new discoveries. It turns out not all faults are simple fractures near the surface on dry land. Unlike the glaringly obvious San Andreas in California, where two plates are sliding past each other horizontally (where a geologist could easily stand with one foot on the North American plate and the other on the Pacific plate and straddle the fault to study it), these offshore rupture zones remained a mystery. Was the boundary between two plates always vertical? Or could one plate slip underneath another? And if so, at what angle? How could you prove it one way or the other? These were just some of the unknowns that would generate a spirited exchange in the coming years.