PSU Magazine Summer 1989

Earth's fragile balance--------------------------- Finding fault with Portland 0 regonians are lucky. Sure, we have more grey days than most of the country, but we don't have tornadoes like the Midwest, we don't have dust storms li ke the Southwest, and we are in no danger of a major earthquake like Cali fo rnia. Right? Wrong, according to Ansel Johnson, head of PSU's Department of Geology. Portland and other parts of Western Oregon have all the makings of a sizeable earthquake sometime in the future, Johnson said. Just how big or how soon is nearly impossible to tell , but he suggests one simply look around to see that the area has gone through some huge shifts in its geologic history. The mere presence of the Cascades shows the effects of plate tectonics, the term given to the movement and interac– tion of the large fl oating masses that make up the earth's lithosphere. In the Nor– thwest, a plate in the Pacific Ocean is mov ing under the plate on which Oregon and Washington sit. The resulting fr iction and the depth at which the Pacific plate is mov ing creates heat, melts rock, and forces magma to the surface in the fo rm of volcanoes. As recently as 1980 when Mount St. Helens blew, the world was reminded that this area is still moving and changing. Geologists over the years have assigned numbers to all the areas of the United States to indicate the level of earthquake danger. California has a high rating, but Oregon's is relatively low, even compared with close neighbors such as Seattle. Structural engineers base building stan– dards on these ratings to assure a structure can withstand the shock of whatever might hit the area. After years of mapping Northwestern Oregon for underground faults , Johnson is convinced Oregon should have a higher rating. Structural engineers don't like the idea, but Johnson said enough evidence exists to justify closer attention to the danger. PSU 6 Geology professor Ansel Johnson uses a gravimeter to measure ground density. "We're try ing to get them to recognize that at least there is a poss ibility," he said . A conference among geologists and engineers was held in Portland this spring to address that very danger. Johnson's studies of assessing earth– quake hazards began in 1974. In 1979 he worked part- time fo r the U.S. Army Corps of Engineers to map underground faults as part of the Corps' engineering of dams throughout the state. The mapping is done with a gravimeter, a device often used for exploration by the oil industry. The gravimeter measures the relative density of the ground on which it sits. By mov ing it to various locations, scientists can map the presence of low density rock next to high density rock. Such contact, or layering, gives strong clues to the geologic activity of the past, shows the presence of faults, and gives some indication of what may be in store for the future. The mapping he has performed along with PSU geologist Marv Beeson shows the presence of faults in the Portland Hills and in the Portland basin . The Puget Sound area has had a much more active earthquake history than Portland : an earthquake measuring 7.2 on the Richter Scale in Seatt.le in 1949, and a 6.5 quake in Tacoma in 1965. But until recently, geologists thought that earthquake danger in that area was confined to Washington alone, and that Oregon presented a wholly different , less dangerous picture. Johnson and his colleagues have found enough evidence of deep underground faults and seismic history in the Portland area to believe that the same danger assessments applied to Seattle should also be applied to Oregon . The fact that Mount St. Helens erupted nine short years ago is evidence enough that the underground plate movement that created the Cascades - called subduction - is still active. ''And Mount St. Helens is just a gnat's eye from Portland ," Johnson said . Johnson and his colleagues have had great success in finding deep underground faults. Still eluding them are the surface 'faults, for which they will be searching over the next two years. "We know they' re there," he said . "They have to be there in order for quakes to occur." In time, because of the PSU Geology Department's successful mapping of underground dangers, Portland may well see tougher building standards, ones that will make buildings more survivable against the big quake from which we thought we were all safe. D The chemistry of smog T he acquaintance Portlanders have with excesses of smog in their air is slight enough that they can still brag about the quality of living and breathing here. Only for two or three days a year does it get bad enough to be harmful . Los Angeles, on the other hand , ex– ceeds the National Air Quality Standards for pollution levels one day out of three. One reason is the far greater number of