5.3 Quake Hits Eureka Area : Temblor: Damage is considerable in several Humboldt County towns. Most injuries are minor.

A magnitude 5.3 earthquake struck before dawn Monday near Eureka, causing about 25 minor injuries, littering the downtown area with glass and producing considerable damage in several communities in Northern California’s Humboldt County.

Emergency authorities said seven homes were red-tagged as unsafe and their occupants were moved to shelters after the 6:10 a.m. temblor, which occurred 11 miles beneath the surface on the Gorda tectonic plate, 12 miles southwest of Eureka.

California’s North Coast--where three plates floating on the Earth’s mantle intersect--has been shaken repeatedly in the last 15 years, with four quakes measuring at least magnitude 7. But all of these have been off the coast and at a greater distance from Eureka.

“A quake closer to home seems stronger,” said Lori Dengler, a Humboldt State University seismologist. “And this one struck with a large closing jolt, and a lot of people say they saw flashing lights, not an uncommon phenomenon in some earthquakes.”

“It hit really hard,” said Eureka resident Jean Gordon. “We were still in bed asleep and it woke us. It broke a few things in the house. We had shelves come down, but there was no damage to anything that was important.”

Gordon said she and her husband later drove through the city of 25,000 on the overcast and drizzly day and saw “quite a few big bay windows shattered and some evidence of landslides.”

“It created a total mess,” Jonathan Webb said of his neighborhood. “I can hear people hammering and pounding and putting things back together.”

Gary Fallan, a spokesman for the Humboldt County Office of Emergency Services, said that the county courthouse, which had been undergoing retrofitting, was damaged and that three towns--Arcata, Fortuna and McKinleyville--had some damage. Chimneys fell at several homes in and outside Eureka, he said.

Three hospitals told Eureka police that injured people, a few with fractured limbs, came to their emergency rooms for treatment. At St. Joseph’s Hospital, emergency generators were used for an hour when power failed, and even hours later, the facility’s computer system remained out, a spokeswoman said.

Bill Walser, a Eureka city spokesman, said that aside from the injuries, a gas line rupture caused the most trouble. The street had to be ripped up by workers seeking to locate the leak, he said.

Fallen merchandise caused two major stores in the city’s malls to close for cleanup on the first shopping day after Christmas, Walser said.

The city’s fishing pier appeared to sustain “a very minor movement away from the shoreline,” he said, and there was a broken waterline at the pier. But the public was still being allowed on the pier.

Dirt and mudslides on U.S. 101 did not interrupt traffic and scattered power outages were cleared up quickly, Walser said.

He said one man was arrested on suspicion of looting after he was found with merchandise from a store whose window had been shattered.

The earthquake was felt as far away as Grants Pass, Ore. Allan Lindh, a scientist with the U.S. Geological Survey at Menlo Park, Calif., called the quake unusual because it was on the tectonic plate itself rather than on one of the plate boundaries.

“Not too many quakes have been felt at this particular location,” Lindh said. “But it’s part of a pattern of increasing activity in the Gorda plate north of the Triple Junction,” where the Gorda, North American and Pacific plates come together and California’s greatest fault, the San Andreas, first comes ashore from the Pacific Ocean.

In 1992 and on Sept. 1 of this year, major temblors, measuring magnitude 7.1 and 7.2, occurred near the Triple Junction and were related to subduction zones, where the leading edge of one plate is slowly submerging and burrowing under another. But Monday’s was not a subduction zone quake, Lindh said.

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Earthquake Location

A magnitude 5.3 earthquake, centered 12 miles southwest of Eureka, occurred early Monday. It caused considerable minor damage in Eureka and surrounding towns of Humboldt County.

Date Magnitude Epicenter Damage Nov. 8, 1980 7.0 Near Eureka 6 injured, freeway overpass collapse Aug. 17, 1991 7.1 Near Crescent City None April 25-26, 1992 7.1, 6.5, 6.2 Near Cape Mendocino 356 injured, $48 million damage Sept. 1, 1994 7.2 Near Cape Mendocino Minor