Waiting for the Big One
The Earthquake and Tsunami That Could Devastate North America
by Jerry Thompson
$26.00 List Price
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