Earthquake Damage and the Home Response Tool

jill's picture

I grew up in earthquake country – otherwise known as the Los Angeles greater metropolitan region – and lived through dozens of “felt” earthquakes. Before the magnitude 6.7 Sylmar (San Fernando, CA) earthquake of 1971, I thought earthquakes were kind of fun. Of course, I was still a teenager, and thought I was invincible. A little “jiggle” now and then made life a little spicier, and no real damage occurred from the mild, infrequent events spanning most of the 1940s, 1950s, and 1960s.

Up until the Sylmar event, Southern California had been in what earthquake scientists call a “quiescent” period (means just what it sounds like: quiet). The Sylmar quake, which struck at 6 am one February morning,  killed 65 people and greatly damaged or even brought down many structures, including a hospital.  That was a real wake up call for southern Californians. Through the next couple of decades, damaging earthquakes increased in that region, and homeowners and business owners alike were continuously at risk, without much information or any tools to help them better protect their lives and properties.

Enter OpenHazards.com. Now anyone, anywhere in the world can come to this website, enter any location they choose,  and immediately receive the kind of information that was only available if one hired an engineering geologist or earthquake hazard risk assessment professional. There’ll be more of these kinds of articles as we build the site, but for now I want to briefly explain what the Open Hazards “Home Response” tool gives you.

First, click on the link “Home Damage Estimator” (under “TOOLS”) on the upper menu bar. The first thing you see is “Calculate your home response to strong earthquakes in three easy steps.” Then you see the line, “Damage Factor: 0.0000”. The damage factor will be calculated based on your home location (how near or far from a potential earthquake fault), building type, and estimated value of the home. The tool uses the damage factor to figure out how much money you can expect, on average, to experience in loss from any size earthquake you choose. You can run as many scenarios as you want, and the tool will calculate your average expected loss for each.

After entering your address in the window below the map (or dragging the little green house to your desired location), go to step 2. You should see some information about your home, which is pulled from public sources such as Zillow.com. If the information you see is correct, you can go to the next step. If not, you can change it. Most homes, by the way, are “wood-frame”, as well as most modern apartment buildings. If you don’t understand the terms for types of construction, you can Google them. For example, a “URM bearing wall” is an unreinforced masonry (such as brick) wall that provides vertical support for a floor or roof.

The last step is simple: choose the size of the earthquake, such as magnitude 5.8 (anything over magnitude 5 will usually cause some damage), and drag the red icon next to, or on top of, your building. Then click “create report.”

What you get is something like this:

"Your test earthquake produced a simulated peak ground acceleration (PGA) of 30.102%g at your home location. Given your description, the damage factor (DF) for this event is 0.3052. This means on average you would experience $77,000 in damage (assuming a home value of $250,000)."

In my next blog entries, I’ll talk more about building types, peak ground acceleration and “g” forces, and the term probability. All these terms may seem unfamiliar, but understanding them will help you better understand how to make decisions about protecting your life and property from a severe, damaging earthquake.

Comments

DavidAlexander's picture

Yes, open hazard is one of the most unique and wonderful websites I have ever seen. In grademiners.com, one could find such information but this is too extensive even for them. Great work by the staff and one cannot leave without appreciating their efforts to save lives.

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