Quakes have history of rockin' 'Boat

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Much of Northwest Colorado shook violently Feb. 10, 1955, when an earthquake later determined to be of intensity VI originated on one of the area's many faults.

The tremor made news in the Feb. 17, 1955, issue of the Steamboat Pilot:

"An earthquake tremor shook Steamboat and most of its residents last Thursday morning. ... The quake was felt in many parts of Northwest Colorado, rattling houses and stores in Kremmling, Oak Creek and Hayden. From Rabbit Ears Pass, it appeared there had been a huge explosion in the Steamboat vicinity, but a check by officials disproved this theory.

"Firsthand accounts suggest the quake was strong enough to crack the plaster of many homes and shake dishes from tabletops, said Vince Matthews, the state geologist and director of the Colorado Geological Survey."

The 1955 quake was the biggest earthquake to hit the Steamboat area in modern times. Several weeks ago, Steamboat shook again, reminding residents that earthquakes are anything but unheard of here.

Just before midnight Sept. 30, a magnitude 3.9 earthquake jolted Steamboat. It was followed by a magnitude 2.2 quake Oct. 9.

Since 1895, 12 earthquakes of magnitude 2.2 or larger have originated on faults found throughout Routt County, according to the Colorado Geological Survey. Three other quakes ranging in magnitude from 3.0 to 3.9 have originated just outside county boundaries: two in Jackson County, including the 3.9-magnitude quake that struck Sept. 30, and one in extreme northern Garfield County.

Earthquakes are measured by intensity and magnitude. The intensity of an earthquake, written as a Roman numeral, describes the severity of an earthquake in terms of its effects on the Earth's surface and on humans and their structures. Magnitude is a number that characterizes the relative size of an earthquake based on the maximum motion recorded by a seismograph.

The epicenters of both recent quakes were northeast of Steamboat in the Buffalo Pass area. The larger quake was on a fault that starts several miles north of Steamboat and runs along the Park Range, Matthews said.

The temblors undoubtedly have left some people wondering when the next jolt will come and how big it will be.

Unfortunately, they'll have to keep wondering -- no one has ever predicted a major earthquake.

Even along California's massive San Andreas Fault, which is the best studied and most intensely monitored fault in the world, there is no way to predict a quake. And having several small earthquakes in a row does not mean another one is coming anytime soon.

But Matthews is confident Steamboat will experience an earthquake again -- and eventually, a moderate or larger earthquake will do the shaking.

"We don't know when or where, but we do know it will (happen)," he said.

Science behind the quakes

Earthquakes are caused by sudden slips on a fault. A fault is a fracture between two blocks of rock that allows the blocks to move. When they move quickly, an earthquake results.

Stress from within the earth, along with the weight of the Earth's crust, push the blocks together. The blocks press and press until so much stress is built up that they slip and release energy in the form of waves that travel through the Earth's crust.

It's similar to snapping your fingers, according to information from the Nevada Seismological Laboratory. You push your fingers together and sideways so hard that as soon as the force of friction is overcome, they move quickly and make a "snap."

There are a number of faults near Steamboat Springs, Matthews said. One fault, called the Steamboat Springs Fault Zone, runs along the west side of the valley.

Hot springs found in and around Steamboat most likely are along faults. Water that is heated deep within the Earth rises up through openings in the rock and out through the cracks.

Colorado faults aren't isolated to the northwest portion of the state. There are numerous faults of varying sizes throughout the state. Accordingly, many parts of Colorado have experienced earthquakes.

The biggest earthquake in modern Colorado history struck in 1882. The magnitude 6.6 quake had an epicenter north of Estes Park and was felt as far away as Kansas and Nebraska. If a quake that size were to strike today, models suggest it would cause $2.4 billion in damage, Matthews said.

Protecting your home

One way to keep earthquake damage and costs down is to build homes to withstand the lateral shaking caused by tremors.

James Henry, president of Jake's Drafting Service in Steamboat, said all structures are designed with consideration of seismic activity. According to the Uniform Building Code, the Steamboat area falls into the lowest category of seismic activity.

But homes anywhere can be built to withstand earthquakes. With lateral restraints, a structure can be tied to its foundation and will be more likely to stay still during an earthquake. Such restraints can cost about $500 to $1,000 on a $500,000 house.

Most Steamboat residents choose not to add the restraints -- even small costs add up, Henry said. But those who previously lived in California typically want to make sure every step possible is taken to build an earthquake-resistant home.

In addition to construction techniques, homes also can be protected from earthquake damage through earthquake insurance. Most homeowner's insurance policies do not cover damage from an earthquake. Homeowners can, however, add an endorsement to their policy to cover earthquake damage.

Debbie Aragon, a State Farm insurance agent based in Steamboat, said only one of her clients has earthquake insurance. But the recent quakes here have spurred a number of phone calls from people wondering whether such an endorsement is a good idea.

Aragon said she plans to begin offering the endorsement to clients -- they can always decline it, but at least they will be aware that it's an option.

The cost of earthquake insurance depends on the value of the home. Earthquake insurance costs about $213 a year for a $250,000 home or condominium in Steamboat, Aragon said.

The endorsement from State Farm Insurance carries a 5 percent deductible, meaning a $500,000 house would have to sustain more than $25,000 in damage to make earthquake insurance worthwhile.

The cost of insurance to protect against earthquake insurance is worth it to Bob Collins, a Steamboat resident who moved here from California 15 years ago. He has awoke to a shaking home a number of times in California, so he immediately bought earthquake insurance for his Steamboat home. Although the policy is yet to be used, Collins thinks it's a good investment.

"It's never worth it until you need it, and if you don't have it when you need it, it's too late," he said.

Matthews, however, thinks most wood-framed homes would fare well in an earthquake. The shake might cause a considerable mess inside the home, but there likely would not be major structural damage, he said.

The cheapest insurance, Matthews said, is something anyone can take out -- don't hang anything heavy on the wall behind your bed.

"That's cheap, and it's probably the best thing you can do to protect yourself," he said.

-- To reach Susan Cunningham, call 871-4203 or e-mail scunningham@steamboatpilot.com

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