Today: November 27, 2001 at 0:55:22 PST

Quake Swarm Keeps Spokane Rocking

SPOKANE, Wash. (AP) - The temblors come day and night. Schools hold duck-and-cover drills. Workers in downtown high-rises study evacuation plans.

For the past six months, Spokane has been in the throes of what experts call an "earthquake swarm." More than 75 have been recorded since May 24, and dozens more could not be measured because of a lack of seismographs.

There have been no injuries or major damage - other than bricks falling from chimneys and items tumbling off shelves - but nerves are fraying.

"We've felt every single one of them," said Cindy Burrows, who works on the 19th floor of the Bank of America Financial Center, downtown's tallest building. "The building doesn't sway. It jumps."

One quake caused such a jolt she had to hang onto her desk, Burrows said.

The high number of earthquakes was unexpected in a metropolitan area thought to be on solid ground, experts say. While none has registered more than a magnitude 4, scientists have no real idea if a big one is looming.

"If they get much bigger, we will start seeing more serious damage," said Tom Yelin of the U.S. Geological Survey, which has sent additional equipment and people to Spokane to study the phenomenon.

The Spokane swarms are part of an active earthquake year. On Feb. 28, a magnitude 6.8 earthquake in the Seattle area injured more than 400 people and did billions of dollars worth of damage. In the past month, hundreds of small earthquakes have been detected near Mount St. Helens, also in western Washington.

But Spokane, a city of 190,000 in eastern Washington, has had no major earthquakes in its 120-year recorded history and wasn't regarded as being in an earthquake zone.

Because of that, there were no seismographs in the city when the earthquakes started in May. Now there are four. Scientists hope the devices will help them locate a fault line that so far has escaped detection.

Bob Derkey, a geologist with the state Department of Natural Resources, believes a fault lies along Latah Creek, in a nearly straight line running southeast across the city. Others aren't as sure.

Nearly all the quakes have been centered on the city's north side. They have been shallow, sometimes only a mile or two deep, and noisy.

Most begin with sounds like explosions or the pounding of heavy equipment - disconcerting noises in the tense atmosphere following the Sept. 11 terrorist attacks on the East Coast. The ground movement generally lasts only a few seconds.

Spokane sits on hard rock between two major seismic areas: the Puget Sound to the west and the Intermountain seismic belt to the east in Idaho and Montana.

The city recorded small earthquakes intermittently from 1915 to 1962, with the largest quake in eastern Washington in the past 100 years being a 5.5-magnitude temblor in 1942 centered 35 miles northeast of Spokane. But nothing in the records shows earthquake activity as energetic and prolonged as this sequence, Steele said.

The lack of recorded major earthquakes in the area is not a source of comfort, because the area's recorded history is just a blink in geologic time, Yelin said.

In addition, such earthquake swarms are little understood, he said.

The strongest quake in the current swarm occurred on Nov. 11, a magnitude 4 temblor that was followed by quakes measuring 3.1 and 3.3 over the next few hours.

"There's no way to say if it is a harbinger" of a bigger quake, Steele said. "We can't rule it out and can't say if it is."

Lack of information about the location and length of the fault is a problem, Steele said. "We don't understand the fault's parameters, so we don't know what the maximum earthquake would be on that structure," he said.

The Spokane quakes have been so shallow that even a magnitude 5 could cause plenty of damage, Steele said. Spokane's downtown also includes a large number of historic buildings, like the 15-story U.S. Bank Building, which was constructed in 1910, that were built long before modern earthquake codes were developed.

At Gonzaga Prep High School, located directly over some of the quakes, the 970 students have been participating in earthquake drills as a precaution.

"Get away from the windows, get into the lowest position and stay there," dean of students Roger Cilley advises them. "We don't want them running out of the building."

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On the Web:

www.ess.washington.edu/SEIS

-- Anonymous, November 27, 2001

Answers

Oddly enough, I was going to move to Spokane at one point, and things suddenly fell through. A week later, I read an article about the increasing changes of major earthquakes beginning to develop in that area around 2000. I laughed and forgot about it until recently.

-- Anonymous, November 27, 2001

I have lots of relatives around there. having heard of anyone getting hurt as yet, or any property damage.

Bet they wish the ground would hold still, tho. hard enough to get around with all the rain...

-- Anonymous, November 27, 2001