Recent quakes cause concern
Earthquakes can be heard, felt and seen many ways. From the slightest vibration to a cataclysmic and violent international disaster, they occur all over the world every day, and with little warning.
The recent small quakes in Truckee, fortunately, have caused minimal damage.
Nevertheless, to help bring attention to earthquake preparedness, the state of California has declared April Earthquake Preparedness Month.
How likely is a major earthquake so high in the Sierra Nevada, anyway?
“There are some very well documented, active faults in Lake Tahoe,” said John Anderson, director of the Nevada Seismological Laboratory in Reno. “Geologists here believe that the underwater faults have the capability to cause a large earthquake, but any of the faults in that area have that potential.”
One of Truckee’s largest earthquakes occurred Sept. 12, 1966, near Boca Reservoir. The quake measured 6.0 on the Richter scale and caused extensive damage, such as toppled chimneys, cracks in two local dams, warping of the highway, railroads and water flumes.
“Truckee is sort of in the transition between the low potential of the valley and the high area to the east,” said Tousson Toppozada, an engineer with the Department of Conservation, Division of Mines and Geology. “The potential in Truckee is not especially high. It’s higher as you go further east toward Reno and Carson City.”
But earthquakes have been rattling the area recently, one last month measuring 3.7 on the Richter scale and another last December measuring 4.9 at the lab in Reno.
So how well prepared are you if an earthquake hits? Better yet, how safe is your home?
“The codes have been upgraded significantly in recent years,” said Elizabeth “Buff” Wendt, a civil engineer with FNW Civil Engineers in Truckee, of the design requirements mandated by the state to ensure homes and buildings are constructed using recent theory on earthquake stability.
Design engineers like Wendt are provided with regional criteria established by the International Conference of Building Officials. California typically adopts the international guidelines every three years.
The Sierra Nevada, in particular, has strict design requirements because of the weather.
Buildings in Truckee have to be tied to their foundations using special clips such as hold-downs and anchor bolts. Wood is often used in place of steel or concrete because it is more resilient to damage caused from movement, Wendt said. Other design requirements include sheer walls, or spatial boards covering the area of the house to make the walls stronger.
Mitch Clarin, president of the Contractors Association of Truckee Tahoe, knows the design requirements well. Not only have the codes added a new level of complexity to the building process, but they have made it more expensive too.
“When contractors talk about the codes getting tougher 90 percent of it is earthquake related, and it’s tougher up here because of the snow load,” he said.
The code describes virtually everything in the building process, Clarin said.
Wendt said builders are inspected rigorously by the local municipalities or counties, who often take an active role evaluating the engineering schematics before the plans are approved.
“If you can build your house to code in Truckee you can build it anywhere,” said Clarin. “In my opinion we have some of the strongest houses anywhere.”
Clarin further stated that the codes may be excessive, and could be causing unnecessary measures. “There is a trade-off when the balance becomes economically unfeasible. I think the codes are overdone, and they are getting worse.”
For more information about Earthquake Preparedness Month, what to do during an earthquake, or other valuable information, check out the state’s office of emergency services Web site at http://www.oes.ca.gov.
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Motorists can expect to see roadwork projects throughout the area this week.