Do you know your earthquake risk exposure and what you can do to reduce it?  Most people don’t.  In this article,  I will talk about your earthquake risk related to where you live:  Your home.  Your earthquake risk related to where you work (which could be substantial) is not addressed here.

“Risk” is the probability of certain consequences occurring.  For example, your life-safety risk from earthquakes is the likelihood that you may die or be injured in an earthquake.  Similarly, your financial risk is the likelihood of certain financial losses that you may suffer as a result of direct and indirect effects of earthquakes.

I am not aware of anyone ever dying in California in a wood-framed single-family house as a result of an earthquake (there may have been some injuries).  So, without going into highly technical analyses, we can say that the likelihood of you dying in your wood-framed house in California during an earthquake is negligible (I admit that I am a bit concerned about the future in light of the recent tsunami in Japan).  However, your financial risk can be substantial depending on the location and characteristics of your house.

Earthquake risk arises from the “direct” earthquake effects on your house, such as the damage caused to your house by ground-shaking,  and from the “indirect” effects, such as the damage caused to your house by liquefaction, ground deformations near the earthquake faults, landslides, tsunamis, fires, and inundation due to failures of levees and dams.  Changing the characteristics of your house by seismic retrofitting can reduce your risk only for the damage caused by ground shaking.  I will talk about seismic retrofitting in the future.  Let us consider now your risk exposure due to the indirect effects of earthquakes, which are primarily location-related.

There is very little you can do to protect your house from liquefaction, ground deformations, landslides, tsunamis, firestorms, and inundation that may follow an earthquake.  You could perhaps reduce the landslide potential by constructing retaining walls at your site, and improve the fire-resistance of your house by changing its roofing and exterior siding to fire-resistant materials.  Otherwise, the only way you can reduce your risk from indirect effects of earthquakes is to buy earthquake insurance (of course, you can also buy a house in an area that is not subject to any of these earthquake-related hazards).

Association of Bay Area Governments (ABAG) provides all the information necessary for home-owners to determine, at least qualitatively, whether their houses are subject to any risk from the indirect earthquake effects of earthquakes.  At their site “Earthquakes and Hazards Program,” you can find the various maps that will tell you if your house is located in a potential liquefaction zone, inundation zone, etc.  If your house is located in one of these hazard zones and the total loss of your house is something you could not or do not want to deal with, do yourself a favor and buy earthquake insurance.  Do it today, as today might be the day we will be hit by the “Big One.”