The Next Tsunami: Living on a Restless Coast

23: Drawing the Line

182 23 Drawing the Line Hillsboro, Oregon, 1995 Earthquake! The ocean roars. Look! Here comes a tsunami. –Warning inscribed on monument memorializing the 1933 Sanriku tsunami at Misawa, Japan The first official Oregon coast tsunami inundation line—geologists’ best guess at how high the water might rise in a typical local tsunami from a typical Cascadia Subduction Zone earthquake—was drawn in 1995. Unless you count Al Aya’s wave form charts that the Clatsop County sheriff had distributed to coastal homeowners from Astoria to Arch Cape back in 1993. But Aya, a statistician, and Visher, an engineer, were amateurs; their estimates of tsunami inundation, while useful, weren’t really scientifically sound. And Clatsop County represented only about one-tenth of the state’s coastline. The Oregon Department of Geology and Mineral Industries had an entire 362-mile-long shoreline to deal with. DOGAMI’s director, Don Hull, had helped organize the Monmouth meeting of geologists in 1987, and it was he who had led transformation of the agency from one focused on extracting natural resources to one with an emphasis on mitigating natural disasters. Now Hull started lobbying the legislature to get serious about setting new seismic standards for building codes in Oregon, not unlike those already in effect in California. But Oregon had another problem, one most of California did not have. Not only was the earthquake scientists were now expecting off the Pacific Northwest coast likely to be bigger than anything the San Andreas Fault could kick up—an apocalyptic quake, as Brian Atwater had described it— but the earthquake rupture zone was underwater. That meant that the Pacific Northwest’s next big quake, like those of the past, would almost certainly generate a large tsunami as well. The subduction zone that could cause such a quake stretched from Vancouver Island down to Cape Mendocino, California, just south of Eureka. It was theoretically possible that a tsunami drawing the line 183 could strike the California coast south of Eureka—the San Francisco area, Los Angeles, and the rest of southern California—but it would necessarily be relatively small. An earthquake on the San Andreas Fault could shake hard enough to cause underwater landslides, which in turn could trigger tsunamis that might do some local damage. And all of California was vulnerable to distant tsunamis from big earthquakes far away, the eastern Aleutian Islands, for example. But a distant tsunami would never be a major disaster. With no subduction zone south of Eureka, most of the California coast is immune from a significant local tsunami of the kind for which Oregon and Washington and Canada’s Vancouver Island had begun bracing. Hull got to work in 1995 lobbying the Oregon legislature, which—in a rare demonstration of unity and resolve—took his advice and, in one session, passed Senate Bill 379. The bill was designed to keep new hospitals and schools and other key public buildings on the coast from being built in the most vulnerable locations—low-elevation sites likely to be inundated in a local tsunami. How low was too low? The legislature left that to DOGAMI to decide—quickly. By summer 1995 the ball was back in DOGAMI’s court. The agency was directed to draw a line to guide new construction along the entire Oregon coast, based on the expected run-up of a local tsunami, and get it done before the end of the year. The job fell to George Priest, the earnest, soft-spoken staff geologist who led the agency’s coastal hazards program. On paper, he was perhaps an unlikely candidate. Priest’s doctorate from Oregon State University was in volcanology. He had worked as an exploration geologist and had taught geology briefly at Portland State University. When he joined DOGAMI in 1979, he went straight to work as a geothermal researcher, and he spent the next decade mapping the heat flow of the Earth throughout Oregon’s interior. But change, and the ability to flex and retool, had characterized his education and his career path. His undergraduate years at OSU—1967 to 1971—had spanned what was perhaps the most intense period of change in the history of the earth sciences, and he could still recall the wonder he had felt reading Tanya Atwater’s seminal 1970 paper on plate tectonics—the sense of everything falling into place. Shortly after the 1987 Monmouth meeting, Priest had become the agency’s point man for earthquake hazards in Oregon. But it was...