After the tragic earthquake and tsunami of March 11, huge areas of Japan were devastated, leaving many people wondering, “Could this happen to California?”
Is southern California overdue for a large earthquake? Saddleback geology instructor James Repka provides an answer.
“I don’t like the term ‘overdue,’ because it implies that there’s a schedule that we can figure out,” Repka said. “But, inasmuch as strain has been building up along the fault since , it would be good if we were prepared for a big earthquake sometime in the next few decades.”
1857 is the year the Fort Tejon earthquake struck southern California. It was approximated to have been at a magnitude of 8.0 on the Richter scale, but the tremor occurred before the system was implemented in 1935.
“Magnitude refers to the energy released by an earthquake. This will always be some percentage of the total energy stored as frictional strain along the fault,” Repka said. “A one point difference [on the Richter scale] indicates a 32-fold increase in energy released. So a magnitude 6.0 earthquake is 32 times more energetic than a 5.0 earthquake, and approximately 1000 times more energetic than a magnitude 4.0 earthquake.”
In addition to the earthquake itself, Orange County will be at significant risk if the San Onofre Nuclear Generation Station is damaged. San Onofre is rated to not sustain significant damage from an earthquake over 7.0, according to officials at the plant. If it were to leak radiation, the majority of south Orange County would have to evacuate due to radiation exposure, as the minimum safe distance is 35 miles from the plant.
So what does this mean for Southern California? It depends on how far a person or building is from the epicenter, or origin point, of the quake. When the “big one” hits, it will be very disruptive to the area. Roads and bridges may become unusable, water lines are at risk of breaking, and electricity will be disconnected in many areas. The companies responsible for these utilities will not be able to respond immediately, due to damage from the shaking, so many people could be without modern conveniences for some time.
Since Orange County does not have extraordinarily tall buildings, most buildings will not be significantly damaged during shaking. However, ceilings may collapse, and because of that people should be quick to take cover underneath a piece of furniture until intense shaking stops. It is just as important to hold onto furniture as it is to take cover, as one will need the combined weight in order to not be tossed around.
The most important thing to remember during an earthquake is to avoid glass, electronics, and anything that can fall from above. By avoiding these hazards, it is more likely that a person will be uninjured after intense shaking, and will be able to evacuate unharmed. It is also important during intense shaking to drop to the ground and stay low.
Repka did not know the earthquake ratings of the main buildings on Saddleback’s campus.
“The first rule of thumb is that, since earthquake standards are evolving at all times, newer buildings are marginally safer than older buildings,” Repka said. “Because the buildings on campus are mostly much wider than they are tall, they are probably pretty safe under most circumstances.”