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Colossal quake will come New study predicts devastation to people, economy By BETH QUINN GRANTS PASS -- Geologists have some bad news for local ex-Californians who moved north to escape the Golden State's well-known earthquakes. "They're less likely to get the nuisance-type earthquakes. They sure may get a doozy, though," says Frank Hladky, resident geologist at the Grants Pass Field Office of the Oregon Department of Geology and Mineral Industries. That doozy of an earthquake will come from the offshore Cascadia subduction zone, where the ocean-bottom Juan de Fuca plate slides under the continental North American plate, creating earthquakes as large as magnitude 9 that can shake the ground for as long as four minutes. In contrast, the San Francisco area's 1989 Loma Prieta quake, caused by plates sliding by each other on the San Andreas fault, measured magnitude 7.1 and shook for 30 seconds. A new study by the Oregon Department of Geology and Mineral Industries predicts that statewide a magnitude 8.5 subduction quake would kill 100 people instantly, injure 6,700 others and leave 12,400 homeless. In addition, such a quake would leave 54,000 buildings destroyed or extensively damaged, knock out 35 percent of police, fire and emergency operations centers, shut down 29 percent of communications systems and leave 9.3 million tons of debris, an economic loss of $11.8 billion. Economic losses in Jackson County would total $371 million, and 3.6 percent of local structures would be destroyed. In Josephine County, which would be closer to the quake's epicenter in the Pacific Ocean 100 miles offshore, losses would total $776 million with 10.3 percent of structures destroyed. Hardest hit would be Coos County, with economic losses of $1.9 billion and 23.7 percent of its buildings destroyed. "It gives the magnitude of the risk we live with and illustrates the importance of preventive measures to reduce these casualties and damages. This is not Oregon's future set in stone," said Don Hull, director of Oregon's geology department. "It is a problem statement for reference as communities and the state decide what we need to fix." The study used special software produced by the Federal Emergency Management Agency and the National Institute of Building Sciences. The software applies a standard model of structural damage to the soil types mapped in Oregon. Hull cautioned that the estimate doesn't include damage and life loss from tsunami, the waves of up to 30 feet generated by offshore quakes that could devastate coastal areas. And the study underestimates Oregon's actual number of brick or masonry buildings -- the ones most likely to collapse and cause death or injury. Using written records of tsunami kept by Japanese villagers and analyses of tree rings in Oregon, scientists have pinpointed the date of Oregon's last Cascadia subduction quake -- Jan. 26, 1700 -- and estimated the magnitude -- at least 9. That's 900 times more powerful than the 1995 magnitude 7 quake in Kobe, Japan, that killed 5,300. Oregon's subduction quakes occur in 300- to 600-year intervals, scientists say, meaning the next one could happen any time. "They are the largest earthquakes that we have on Earth," said the Oregon Geology Department's Lou Clark. "It's a very long, strong earthquake." Since scientists first became aware of the threat of subduction quakes 20 years ago, Oregon has tightened building codes, required earthquake drills at schools and held tsunami drills on the coast. And in a state where lesser faults such as those near Klamath Falls can deliver magnitude 6 earthquakes, preparations for the rare devastating subduction quake can help minimize damage from more frequent but less destructive quakes. "We have lots of reasons to start getting ready and prepare," Clark said. Among the preparations will be a more in-depth analysis of earthquake hazards in Southern Oregon to help pinpoint where and how to minimize damage. This century's population explosion along the seismically active West Coast has added a new sense of urgency to the geologist's work. "It's seen as being pretty important if you're going to look at the costs of maintaining a civilization on the West Coast of North America," Hladky said. Houses sit on slides; McLoughlin will blow Jackson County's earthquake hazards haven't yet been mapped, but state geologist Frank Hladky and others have spent the past eight years studying other features of the landscape. Among their findings: Landslides likely caused by Oregon's giant subduction quakes are a prominent feature of the Bear Creek Valley. The Oregon Department of Transportation built an Interstate 5 visitor center atop one landslide on the Siskiyou Summit grade, and homeowners in the Skycrest subdivision on the flanks of Roxy Ann Peak live on another. "That's why you drive around there and people are always fixing their garage doors," Hladky says. Not to worry, however. That slide may be sinking but it's no longer sliding. The visitor center is another matter, however, which may be one reason ODOT closed it. A third large slide is slipping down the northern flank of Roxy Ann, following the path of Dry Creek. Volcanoes aren't just mountains like McLoughlin or Shasta. Roxy Ann is a volcano, and at 30 million years is one of the oldest in the Cascades. "It's what we call a volcanic neck," Hladky says. "The shoulders and the head are gone." And 20-million-year-old Grizzly Peak offers an up-close and personal view of a volcano. "If you go up Antelope Creek Road, you'll see the interior of a volcano because the stream has literally cut through the guts of it," Hladky says. Those ancient volcanoes are certainly extinct, but at 150,000 years old, Mount McLoughlin is a relative pup -- geologically speaking -- and will erupt again. "It sits in the zone of activity. That would certainly be an issue for Klamath Falls; that's downwind of the ashfall," Hladky says. Minerals such as gold and copper may be associated with volcanism, but so are mercury and arsenic. A complex of silica-rich volcanoes south of Lake Creek have laced the area with mineral-rich and potentially toxic springs. One near Soda Creek had an arsenic level high enough to kill livestock drinking from it, Hladky says. Mail Tribune Copyright � The Mail Tribune 1998, Medford, Oregon USA