San Diego’s Earthquake Risk
If you live in middle America, or pretty much anywhere outside of California, you probably think that San Diegans must stay up nights, worried about earthquakes tossing us into the sea. Well, we don’t.
Why? See the map at right. This is a historic map of earthquakes in Southern California. As the map illustrates, San Diego has never experienced a truly large earthquake (at least not since 1862, when it is believed a 6.0 magnitude earthquake damaged Old Town).
Sure, we do feel a tremor now and then, but they tend to be small and/or distant. We’re used to them. Some of us even like them.
California’s most famous fault, the San Andreas (pictured at left), avoids San Diego County entirely, swinging eastward through Imperial County, before ending in the Salton Sea. When an earthquake hits along the San Andreas fault, it may be felt in San Diego, but what we experience is a small shaking sensation that starts and stops in under 30 seconds. We hardly have time to run for a doorway.
In June of 1983, San Diegans were shaken out of bed by an earthquake measuring 4.6 on the Richter scale.. It was centered in the Pacific ocean, about 10 miles from the US/Mexican border. Although that was the largest earthquake measured until that time, little damage was reported.
Three years later, San Diego experienced an even larger earthquake, with a magnitude of 5.3, felt along much of Southern California’s coast. Again, little damage here. This is because the epicenter was in the ocean, about 28 miles southwest of Oceanside, on what is now known as the Oceanside fault.
A 5.2 magnitude earthquake hit 49 miles southwest of San Diego (see map at left) in June of 2004, on or near the San Clemente fault. Other than temporarily shutting down amusement park rides throughout the county, and sending engineers out to check bridges and railroad tracks, the earthquake created little disruption.
That’s about all we’ve experienced of earthquakes in San Diego.
Other San Diego Fault Zones
Scientist consider the Rose Canyon fault zone to be our most serious at present, because it lies under the city of San Diego, running across Mission Bay, under Mount Soledad, and into La Jolla Cove. A large earthquake through these populous areas could be devastating.
The San Jacinto fault zone is also of great concern. It runs through Borrego Springs, and geologists are worried that it may prove more dangerous than the San Andreas Fault in the long run.
Additional earthquake fault zones in our region include the Coronado, Descanso, Elsinore, Florida Canyon, La Nacion, Newport-Inglewood, Old Town, Palos Verdes, San Diego Trough, Silver Strand, South Coronado Bridge, and Spanish Bight fault zones. Individually, these faults each pose some earthquake risk. In combination, they may actually multiply our risk. For example, scientists have theorized that if the Oceanside, Rose Canyon and Newport-Inglewood faults all ruptured at the same time, it could produce a magnitude 7.6 quake.
So Why Aren’t We Worried?
Our homes have been built to withstand earthquakes for some years now, so most will survive considerable shaking. Our water heaters are usually strapped down when they’re put in (for those who aren’t yet using a tankless), and if you grow up here, you know to use putty or sticky tape under statuettes and other objects likely to break in a fall. Some install child safety latches on china cabinets or anchor larger cabinets to their walls ”just to be on the safe side,” but many don’t bother. We prepare for earthquakes when it’s convenient, never really believing the big one will hit here.
San Diegans are a lot like Floridians who remain on the east coast, no matter how many hurricanes hit, or Oklahomans who endure tornadoes year after year. When it comes to natural disasters, we all prefer the ones we know to the ones we hear about on the news; they always sound so much worse. San Diegans also rationalize that, unlike tornadoes and hurricanes, it doesn’t make much sense to worry about impending earthquakes, since there’s no warning for them, and little preparation one can do ahead of time anyway.
Besides, we love to ride a good wave!
For further information:
Scripps Institution of Oceanography: A Seismic Jigsaw Puzzle Takes Shape
Southern California Earthquake Data Center
Faults and Earthquakes in San Diego County
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