5.7 Temblor Came as a Shock to Oregon Town : Earthquake: Klamath Falls is slowly recovering from strongest jolt since at least 1860. Ex-Californians consider moving again.

With the county courthouse and library shut by safety engineers and much of the downtown area still cordoned off, Klamath Falls, Ore., was recovering slowly Tuesday from earthquakes that resulted in two deaths and collapsed the facades of several brick buildings.

The U.S. Geological Survey upgraded the magnitude of Monday night’s largest temblor to a moderately strong magnitude 5.7 and said it had been followed by other shocks of magnitude 5.5 and 4.8, all centered along Upper Klamath Lake. The epicenter was approximately 15 miles northwest of Klamath Falls, a city of 18,500 residents about 15 miles north of the California border.

Although such major Cascade volcanoes as Mt. Shasta and Mt. McLoughlin are in the vicinity, scientists said the earthquakes were not volcanic in origin and appeared to be due to normal faulting near the edge of the Great Basin.

It was the strongest earthquake felt at Klamath Falls since record keeping began in 1860. There had never been a recorded jolt stronger than magnitude 4.3. USGS scientist David R. Sherrod noted in his official report Tuesday, “Residents may live in Klamath Falls for 20 or 30 years and never feel an earthquake.”

This made the quakes all the more surprising to some Southern Californians who have moved to the area in recent years.

Steve Anderson, a tattoo shop owner who once lived in La Crescenta and who suffered a broken foot in the 1971 Sylmar-San Fernando earthquake, escaped without injury this time but said Monday night’s experience “reminded me of living in Southern California.”

“I had a lot of friends up here call who didn’t know what it was,” he said. “But I knew immediately. You could see the ground buckle, my car and pickup truck move, and a lot of power lines fell.”

A couple who moved north after the 1987 Whittier Narrows quake, Kathy and Charles Heard, told the Associated Press they may move on to Wyoming. After the second aftershock, they said, they fled their house and joined about 100 residents who spent the night outdoors.

For a time Tuesday, four highways out of the city were closed, but all were reopened after bridge inspections found that damage was minimal.

More serious damage was sustained by Klamath Falls’ brick masonry buildings. A police spokesman said it may be a few days before engineers are able to inspect them all, but he said facades had fallen from at least eight.

Ian Madin, a quake expert with the Oregon Department of Geology and Mineral Industries, noted that in July, Oregon authorities had upgraded the designation of western Oregon, including Klamath Falls, from Seismic Zone 2 to Seismic Zone 3, and begun requiring new construction to avoid using brick masonry, which is particularly vulnerable to quake damage.

“There’s no retrofit requirement in Oregon building codes yet,” said Madin. “It’s hard to find the financing to retrofit.”

California generally grades areas either Seismic Zone 3, or close to major faults, Seismic Zone 4. Some cities, including Los Angeles, do have retrofit requirements for brick buildings.

The two fatalities caused by the main 8:29 p.m. temblor Monday night were Kenneth Campbell, 59, from Phoenix, Ariz., who was driving his pickup on a highway north of town when it was struck by a 14-foot boulder that crashed down in a rockslide, and Anna Marion Horton, 82, of Chiloquin, Ore., who had a heart attack.

Horton’s son said she had been severely frightened by her house shaking before going into cardiac arrest. Campbell’s wife, who was riding with him, did not sustain serious injury.

Sherrod of the Geological Survey said that although 15 earthquakes have occurred within 10 miles of Klamath Falls since 1945, and a fault scarp runs noticeably through the center of town, only seven of the quakes were larger than magnitude 3.

Quake swarms have occurred in similar geologic settings 100 miles away in Oregon’s Warner Valley in 1968 and 45 miles away near Stephens Pass in California in 1978. Both swarms were marked by numerous magnitude 4 and 5 range earthquakes, Sherrod said, adding that it would be reasonable to expect further shocks in Klamath Falls in the near future.