How Much Danger is Your Home or Business In? It is all about location.
If you live in California, the US Geological Survey has said that Southern California will most likely be hit with a big earthquake within the next 30 years. They said that there is a 99% chance that we’ll experience a quake with a magnitude of at least 6.7. They also said there is 46% chance that we will have a 7.5 magnitude quake – or bigger.
So what does that mean for San Diego County residents? Even though the “big one” is supposed to have an epicenter somewhere in Southern California, most San Diego residents are not highly at risk. Well, at least compared to Orange County and Los Angeles (LA) residents. One indicator is earthquake insurance rates. In San Diego versus LA, the average premium cost in San Diego is only $251 per year compared to Los Angeles and Orange Counties which is $693 per year.
According to a recent San Diego Union Tribune article, a ‘Big One’ in California would not be like the recent big quake in Chile. Because California’s seismic plate tectonics differ from Chile’s, our region is not subject to the large magnitude quakes that they experience down there. In California the plates slide sideways while in Chile they slide under each other. Additionally the crust is a lot thinner here than in Chile. Because of those two factors, seismologists predict a maximum 8.1 quake at the worst for Southern California.
The San Andreas Fault, which extends from the Salton Sea to the town of Parkfield in Monterrey County, provides the greatest seismic threat. Luckily though, the Salton Sea area is a long distance away from most San Diego residents. In addition, the San Andreas Fault is inland and would not result in a tsunami, which caused much of the recent damage in Chile. There are several off shore faults near San Diego but they are very small and do not present much risk.
If a big jolt did indeed hit the San Andreas Fault near the Salton Sea, San Diego City residents would definitely feel it, but most likely would not experience catastrophic damage or casualties. Despite that, we do have a few smaller local faults that have the potential to generate a pretty big jolt. The most worrisome San Diego County faults are the Rose Canyon Fault on the east side of Pacific Beach and La Jolla. A little further south and inland, the La Nacion Fault runs through South San Diego, Chula Vista and National City. In East County mountains and deserts, you need to be aware of the Elsinore, Aqua Caliente and San Jacinto Fault Zones.
So, depending on where you live, there is varying danger of fault movement and earthquake shaking. If you live close to a known fault, you should be aware of the possibility of a large jolt damaging your property. However, there are two other risk factors as well, they are landslide and liquefaction. During an earthquake, especially after wet weather, the violent earth shaking may trigger a landslide. However, of more importance is what your home or business is built upon.
Many San Diego homes and businesses are built on sand or on fill and are vulnerable to what is known as soil liquefaction. During a quake these kinds of soils can act like jello, amplifying a quake’s movement more than a home built on rock or settled land. Because of liquefaction, a home that is close to a earthquake epicenter that is built on rock may experience less shaking and damage than a home that is much further away that is built on sand or fill.
How can you find out what is under your home and what danger is neighborhood is in?
A great online resource to check out your specific neighborhood is this online map to find fault lines, landslide and liquefaction zones in your San Diego community http://files.sangis.org/interactive/viewer/Viewer.asp
It’s a little complicated to use this online map. Start by clicking on the “custom map” button. On the right side scroll down and then click on Faults. Next click on Geologic Hazards. That will activate those map layers. Then hit Refresh at bottom of page on the right side.
Now is the fun part – finding your neighborhood. Using the PAN and ZOOM IN controls, navigate around the map and zoom in to find your neighborhood and its geologic hazards for fault zones, liquefaction and landslides. You can zoom in to your specific block to get an idea of the earthquake related threats around your home or business.
If you are clear of all those, you probably don’t need Earthquake Insurance as much as someone whose home is in a liquefaction zone adjacent to an earthquake fault.