Early in the evening of March 27, 1964, a 9.2-magnitude earthquake shook Anchorage, Alaska, to pieces, and loosed a tsunami down the Pacific coast that claimed lives and coastal infrastructure as far south as Crescent City, California. The Good Friday Earthquake, as it was later called, was the largest recorded seismic event in American history, and a young US Geological Survey geologist named George Plafker flew to Anchorage the following day to find the fault line that had caused all the trouble. To his surprise, he couldn’t: There was no jagged vertical fracture in the earth as there would have been following a quake along, for instance, California’s better-understood San Andreas Fault. Instead, the rocks near the epicenter seemed to have folded in on themselves, or stretched apart as if they were putty.
Plafker’s observations suggested a previously unknown type of earthquake, one explained by the then-ascendant theory of plate tectonics. Two of the seven major plates that make up the earth’s crust met along the Alaskan coastline; the contortions in the geology near Anchorage were consistent with one of the plates grinding against and sliding beneath the other. But this conclusion raised an unsettling thought. A similar geologic boundary, later named the Cascadia Subduction Zone, ran along at least six hundred miles of the Pacific coastline, from Vancouver Island in Canada to Eureka, California. That meant that what happened in Anchorage could just as easily happen in Portland, Oregon; Sacramento; Seattle; Vancouver; or Victoria, British Columbiaor all of them at once. As Jerry Thompson writes in Cascadia’s Fault, “Imagine having five Hurricane Katrinas—hitting five different cities—on the same day.”
The best parts of Cascadia’s Fault tell the story of how this threat slowly came into focus: how geologists spent two decades reconstructing the region’s seismically violent past in an attempt to imagine its future. That past arrived in fragments. There were, for example, the “ghost forests”—groves of cedar trees that the abrupt rearrangement of local geology had dropped into the coastal shallows, dead but still standing three centuries after the fact—along the Copalis River in southern Washington. Prefectural records from Japan contained reports of a tsunami of mysterious origin making landfall late one night in the winter of 1700. And decades of surveyors’ measurements showed a slow but unmistakable eastward drift of mountains along the West Coast from Oregon to British Columbia.
These are the makings of a fine scientific detective story. But Thompson, a Vancouver-based documentary filmmaker, is no John McPhee. Thompson doesn’t come off as particularly sure of himself on the science of earthquakes, a serious problem for a book that takes earthquake science as its subject. He also makes the questionable decision to end Cascadia’s Fault with an imaginary set piece right out of 2012 or The Day After Tomorrow, in which Cascadia unleashes chaos throughout the Pacific Northwest. A tsunami pounds coastal communities “like some massive, demonic fire hose”; in the region’s cities, “the same death spiral everyone saw in New York on 9/11 happens all over again” amid the collapsing skyscrapers.
Of course, anyone who has turned on CNN or clicked around YouTube in the months since Cascadia’s Fault went to press needs no help envisioning what a catastrophic earthquake or tsunami looks like. The proliferation of consumer electronics in the northeastern Japanese city of Sendai—and, six years earlier, in the tourist enclaves of Sumatra—has provided ample, and terrifying, footage of a category of disaster that videographers had previously found maddeningly difficult to capture.
The major seismic episodes of recent decades have taught disaster experts a great deal about who dies in an earthquake and its aftermath, who doesn’t, and why, and the deciding factors are often human ones. The temblor that decimated Port-au-Prince, Haiti, in January 2010, for instance, was one five-hundredth the strength of the earthquake that shook Chile the following month, and yet the Haitian earthquake claimed more than five hundred times as many casualties and exacted at least five times the economic impact. This was in part dumb luck—the epicenter of Chile’s quake was in a relatively low-population region south of the capital of Santiago—but only in part. Chile, which boasts more seismologists per capita than any other country, had well-enforced, earthquake-ready building codes, and Chileans were trained in how to react to a quake. The Haitian capital, by contrast, was totally lacking in building regulations and overcrowded with impoverished residents who had no idea what to do in the event of disaster. The two quakes fit a well-established pattern: Seismic disasters kill far more people in poor and disorganized countries than in developed ones.
That’s not much comfort to a great many countries, but it is good news—sort of—for Cascadia’s possible victims. Thompson suggests that the residents and governments of the cities and towns of the West Coast should prepare for a potential disaster by drafting tsunami maps and response plans, as many have. He also notes that most of the tall buildings in the region’s urban areas are not built to withstand the worst Cascadia quake scenarios. This is unfortunately true, but urban planning is a necessarily slow-moving business. Skylines turn over slowly, and rebuilding the entire urban core of the city overnight is simply not in anyone’s budget. Thompson’s nightmare is something that everyone in the Northwest has no choice but to live with, however uneasily.
Charles Homans is an associate editor of Foreign Policy.