Can your house survive the big shake?

June 24--Would your house survive a massive earthquake?

Emergency management officials say the expected Cascadia subduction zone quake could shake the Rogue Valley so hard that houses could collapse or slide off their foundations, leaving thousands homeless, injured or worse.

Even newer houses built before 1993 could see enough damage that they become uninhabitable.

"We could see sustained shaking for two to five minutes that could cause significant damage," warned Althea Rizzo, geologic hazards program coordinator for the Oregon Office of Emergency Management. "Almost all the older homes need some kind of retrofit."

Emergency planners will hold a seminar on how residents can better prepare their houses for the "Big One" from 6 to 8 p.m. Tuesday at Rogue Valley Council of Governments, 155 N. First St., Central Point. To register, go to https://medfordseismic.eventbrite.com.

Builders will be offered a separate seminar from 8:30 a.m. to 5 p.m. Tuesday at the same address that will provide information on the latest requirements for earthquake safety and retrofits. Registration for that seminar is at https://fema-p50-medford.eventbrite.com.

The Oregon Office of Emergency Management provides an extensive list of ways to prepare for an earthquake at http://ow.ly/b74O30kBMmS. Some of the information includes the often-heard advice to drop, cover and hold on when the shaking starts.

Geologists warn that the West Coast is due for another Cascadia earthquake, which rocked this area with a magnitude 9.0 in 1700 and sent a tsunami toward Japan. Previously, a similar quake struck the West Coast in 1310.

In a 2015 article in the New Yorker, Kenneth Murphy, who directs FEMA's division responsible for Oregon, Washington, Idaho and Alaska, issued a dire warning about the Cascadia: "Our operating assumption is that everything west of Interstate 5 will be toast."

While many geologists question the severity of Murphy's assumption, they do believe a Cascadia quake could cut off the Rogue Valley for weeks or even months, with only airlifts bringing in supplies. Many bridges on Interstate 5, including the viaduct through Medford, are expected to crumble.

Rizzo said a basic retrofit for an old house could cost less than $10,000, and the improvements would make it more habitable if an earthquake strikes.

"You may not have power, you may not have water, but at least you can still sleep in your bed," she said.

While the basic construction of a house is important, Rizzo said alluvial soils that predominate in the Rogue Valley aren't the best to build a foundation on.

"Bedrock is best," she said.

Most houses constructed in the last 20 years or so have significant improvements that should help them withstand a quake. Tougher statewide building standards were required after 1993.

Metal plates that attach roof trusses to walls are now standard. Cripple walls, or short walls below the floor to the foundation, have plywood panels that generally are screwed in, rather than nailed on as they are on older houses.

Many recently built houses, particularly two-story homes with lots of windows and openings on a particular wall, also have metal plates that connect the foundation directly with the walls. Some have plates that connect the upper and lower floors.

In general, single-story houses fare better than two-story houses in an earthquake, Rizzo said.

According to the Oregon Construction Contractors Board, some houses built without the latest improvements could suffer significant damage during an earthquake. Some could slide or lift off their foundations. Lack of appropriate bracing in cripple walls could result in buckling or collapse from the racking action of an earthquake.

Costs for retrofitting a basement area vary from $4,000 to $10,000 for a 2,000-square-foot, single-story house, according to the contractors board.

Other concerns include living spaces above a garage or other large openings in the house. Additional bracing may be required to strengthen the garage to make it less vulnerable to racking.

Water heaters are now required by code to be strapped to the wall. (Preparedness hint: The 50 gallons or so in the water heater will come in handy if the water is cut off to the house after an earthquake. A rule of thumb is to have one gallon of water on hand per day for every person in a household.)

On older houses, masonry chimneys, which tend to fall down in an earthquake, may need bracing.

Houses can be retrofitted with an automatic shutoff valve to the gas line between the meter and the house. Once the earthquake strikes, the shaking causes the valve to shut off.

The interior of houses can become a danger zone when the shaking starts. Firmly attach a top-heavy china hutch or other pieces of furniture to a wall.

Even refrigerators in cabinets can roll forward, but you can get shims that prevent the wheels from moving around too much. During the first couple of days of a power outage, you'll be using a lot of food in that fridge so you want to protect it.

Earthquake insurance is another question facing homeowners, though deductibles can be high, leaving you out of pocket by $10,000 or more. The cost can range from $200 to $300 a year, depending on the type of house you have. Masonry buildings typically cost much more.

Preparing for the "Big One" -- especially when there's a good chance it won't happen in your lifetime -- can feel overwhelming.

Geologist Eric Dittmer, a retired Southern Oregon University professor, suggests people start out with simple steps, such as amassing enough food and water to last two weeks or more. A first-aid kit is important, and make sure you have a supply of medications to last for a prolonged period of isolation. Dittmer said he has extra bottles of heart medications on hand.

While he's worried about a major earthquake, Dittmer said he recommends taking small steps to get your family ready.

"Do this a piece at a time," he said. "Don't let it overwhelm you."

Despite preparation, Dittmer acknowledges he may not have done enough at his west Medford home.

"I'm a little nervous about having enough food for a long period of time," he said. "And don't forget to have food for your pets."

Dittmer has taken steps to make his house less prone to damage, including installing braces around his air conditioner to prevent it from sliding around.

His refrigerator is affixed to the wall to prevent it rolling forward, even though it is surrounded by cabinets.

He does have miniature ham radios to keep in touch with his son's family, who lives about five miles away in east Medford, and he's mapped out an emergency route so his son can get to his house.

Dittmer suggests using the exit 27 overpass because it is relatively new and built to the latest earthquake standards. Still, he said he thinks people will be relying on bikes and walking to get around.

He doesn't think Interstate 5 bridges will survive the quake, so he suggests residents use Highway 99 to traverse the valley.

Dittmer also has a "go kit" in his car with water, food and first-aid supplies in case he gets stranded someplace in the valley.

His 1975 home concerns him. After some checking, he doesn't believe the house is bolted to the foundation, but he doesn't have the $10,000 or so it might cost to fix it. As a result, he's thinking of doing the work himself.

Still, Dittmer thinks his house should survive the shaking, pointing out that wood-frame buildings fare better than masonry structures.

Dittmer suggest people get earthquake insurance, though he acknowledges it might be expensive for some homeowners. He said he pays $300 a year but has a deductible of about $30,000.

To give some idea of the strength of the Cascadia, Dittmer said the Loma Prieta earthquake in San Francisco shook for 15 seconds in 1989 and caused widespread damage, including collapsed bridges and freeways. A Cascadia will shake for minutes, though some of the energy will be absorbed by the time it reaches the Rogue Valley from an epicenter along a fault line in the ocean.

State officials expect a 100-foot tsunami will hit the coastline.

Ryan Thomas, director of sales for TerraFirma, said his company does a few hundred earthquake retrofits a year, mostly for former Californians who've had to live through quakes.

Thomas said he's seen many houses built before 1980 in Oregon that aren't attached to the foundation with bolts.

"If someone has a 1990 or newer house, it's probably tied down," he said. "Anything from the '80s or older, probably not."

To get some idea how many houses might not be ready for an earthquake, there were 11,271 houses in Medford by 1970 and 19,684 by 1990, according to city officials.

Often insurance companies won't cover a house if it doesn't have bolts anchoring the house to the foundation, Thomas said.

He said retrofitting the basement of a typical house would cost $3,000 to $8,000.

Reach reporter Damian Mann at 541-776-4476 or [email protected]. Follow him on www.twitter.com/reporterdm.

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