If you feel the earth move under your feet and you wonder if there's been an earthquake, there's a seismograph at Southern Oregon University that can tell you what really happened.

If you feel the earth move under your feet and you wonder if there's been an earthquake, there's a seismograph at Southern Oregon University that can tell you what really happened.

It used to be that the earth's movements were recorded on paper drums by twitchy needles in far-off labs, remote from public view. Now, instruments in a "black box" in Roca Canyon, near the SOU campus, are tied into a network that records movements of the earth's crust all over the Northwest.

The SOU Strong Motion Webicorder is sensitive to quakes over 5.0 on the Richter scale, geology professor Charles Lane explained as he demonstrated how to navigate the Web site. It tracks earthquakes, volcanic activity and movements of the earth's crust that could trigger a tsunami alert.

The SOU device is part of the Pacific Northwest Seismic Network, based at the University of Washington in Seattle. The network is a joint venture of the U.S. Geological Survey, the federal Department of Energy and the state of Washington.

Inquiring minds can look at charts from sites across the Northwest, including Crater Lake, Mount Hood and Newberry Crater, as well as Klamath Falls, Lakeview, Monmouth, Roseburg and the Oregon Coast.

Lane said the network is vital in this part of the world because of the extreme dynamism of the region's geological features. The Cascadia plate of the earth's crust is sliding under the continent, fueling the Cascade volcanoes. There's also plenty of seismic activity in the basin-and-range terrain east of the Cascades, and coastal cities are vulnerable to quake-caused tsunamis.

"There's real potential for seismic events here because (the Cascadia plate) extends from Cape Mendocino to Vancouver Island," he said. "It's a long fault complex " and the longer the fault, the more we're concerned about earthquakes of a larger magnitude."

Lane said big quakes have struck the region every 300 years or so — and it's been that long since the last big one.

"The question is when, rather than if, it comes," he said, noting that there's a large deviation around the time frequency.

A major quake could occur next week or centuries from now, "but the last big one, which was 8.0 (on the Richter scale), was about 1700," he said.

The San Francisco earthquake of 1906 was estimated to be magnitude 7.8 on the scale.

An observer discovered that watching the seismograph can be hypnotic. Its tiny squiggles are like "static" and aren't reading any seismic event, but serious blips occur several times a day — indications, Lane said, of magma moving up and down in tubes beneath the earth's surface.

Lane said the Cascades are still active volcanoes, although there have been few significant eruptions in modern times. Scientists keep a keen eye on Mount Shasta, Mount Rainier and Mount St. Helens because of their proximity to large cities or their recent activity.

Mount St. Helens' notable eruption in 1980 killed more than 50 people and spewed ash across much of the Northwest. Recently, less dramatic activity has been recorded at Sisters, Newberry Crater, Mount Hood and Mount Baker, he said.

Lane said the network was designed to spot quakes that could cause devastating tsunamis and to provide timely warnings of volcanic eruptions in the Cascades.

He said the big difference from the days of the jumpy needle scrawling on the paper drum, is that today's digital seismometers are linked in a global network.

"Virtually any of us who pay attention to earthquakes can jump right online and not have to find a paper copy," he said. "The data distribution is so extensive and speeded up, compared to 20 years ago."

A major earthquake could have severe implications for Oregon, according to a report released in November by the Oregon Department of Transportation. The report said a major quake would knock out most important bridges in Oregon, making Highway 101 and Interstate 5 impassable and isolating the coast from the Interstate 5 corridor.

Seismic retrofitting for bridges would cost an estimated $3 billion, the report said.

"A lot of the bridges and overpasses would be at risk," said Lane, who said he was thrown out of his car by California's Whittier Narrows earthquake in 1987.

There are local hazards, too, he said.

"Right here," he said, "the Mediterranean tile on Churchill Hall, in an earthquake, could kill someone."

John Darling is a freelance writer living in Ashland. E-mail him at jdarling@jeffnet.org.