Shifting and Shaking; How a FEMA earthquake scientist retrofits her home

Written by: Hannah Rabinowitz

As an earthquake scientist, I have spent a lot of time thinking about how earthquakes happen. But since joining FEMA Region 10 in Bothell, WA, last year as the Earthquake, Tsunami and Volcano Program Manager, my concerns about earthquakes now hit much closer to home. Though all four states in Region 10 (Oregon, Washington, Idaho, and Alaska) are considered “high” or “very high” earthquake hazard states, the western parts of Oregon and Washington and the southern portion of Alaska are exposed to the largest types of earthquakes, known as megathrust earthquakes. These earthquakes can reach over a magnitude 9, causing significant damage from shaking as well as triggering large tsunamis that can have impact across whole ocean basins. And it’s not only these huge earthquakes that we need to think about. Living on an active plate boundary, there are lots of faults underfoot.

When you move to an area that has these looming earthquake hazards, you start to wonder what you can do to protect your family. Fortunately, there are lots of steps that we can take, ranging from simple “non-structural retrofits” such as securing bookshelves and water heaters to the wall to more involved “structural retrofits”. As a renter, I was able to take steps such as bolting bookshelves in my house to the wall to minimize the likelihood that they would tip over during an earthquake.

However, this summer, my family bought a house built in the 1950s. When house hunting, we checked out liquefaction maps of the Seattle area and kept an eye on how steep of a slope the house was built on. Hazards like liquefaction and landslides can be hard to retrofit buildings for. We also kept in mind whether the houses had garages underneath living spaces or tall brick chimneys, both of which are fairly common features of single-family homes in the Seattle area and are vulnerable to collapse during an earthquake.

We knew that we were almost certainly going to end up with a house that needed some sort of retrofit, but we wanted to try to avoid more significant structural retrofits as much as possible.

We eventually found a house that met our earthquake safety criteria. Once we had moved in, we got a couple of earthquake engineering companies to come take a look at what needed to be done and provide quotes. The main concern in our house was a cripple wall vulnerability which means the connection between the foundation and the house wasn’t up to current earthquake building codes. Because we don’t have a basement, just a crawlspace, this can be addressed through a pretty simple reinforcement. A cripple wall retrofit aims to make sure that when the ground shakes from side-to-side during an earthquake, the foundation and the house move together so that the house doesn’t slip off of the foundation.

The work includes a retrofit plate that connects the concrete foundation to the sill plate, and then two smaller retrofit plates that connect the sill plate to the rim and the rim to the subfloor.

While doing a structural earthquake retrofit, which includes permits and inspections, was definitely a bigger investment than the non-structural retrofits that we’ve been able to do in the past as renters, it was an important step to take to protect my family’s safety.? It’s also an investment into our house if an earthquake does happen. Additionally, the cost of the retrofit is much less than the cost of having to repair the house if it were to slip off of its foundation during an earthquake. I hope that you take the opportunity to consider retrofitting your home if you have the chance as well.

For some information about how to start thinking about an earthquake retrofit for your house, check out these resources:

·??????? Earthquake Country Alliance – Earthquake Mitigation

·??????? Washington Geologic Survey – Homeowners Guide to Earthquakes