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Mar 10
Drop, Cover and Hold On

occ geology professor erik bender with seismograph ​

​ Professor Erik Bender explains what will really happen when the Big One hits, and how to be prepared

When it comes to teaching his students about the re​alities of a major earthquake in Southern California, Orange Coast College geology professor Erik Bender knows what he's up against. 

With the average age of OCC students hovering somewhere between 18 and 25 years, Bender understands that most of the kids that sit in his classroom each day have never experienced a large earthquake, and those that have were probably too young to remember it. 

Still … he tries. 

"I tell them it's kind of like Godzilla," Bender says. "It's something so big and bad, you almost can't believe its real. People can't fathom the amount of motion and the amount of damage that could happen." 

Fortunately, Bender has the tools to give his students an idea, if only theoretically. After receiving an anonymous $120,000 donation last year, the College installed three seismographs at various locations in the Southland, including one on OCC's campus (the other two are located in Palos Verdes and Laguna Beach.) 

The instrument is solar powered and tethered to the ground with 20-foot-deep posts. OCC's seismographs also include a cell tower and GPS capabilities that would allow for data to be gathered and shared, even if power and cell service went out in the area. 

Bender uses the seismographs and other tools to teach his students about the region's seismic activity, and potential hazards. While its impossible to predict the timing and size of Southern California's next large earthquake, there are still some predictions that seismologists can confidently make. 

For example, of the ever-elusive San Andreas fault — which is expected to break at any time with an earthquake measuring a minimum 7.8 magnitude — Bender says:  "[In this area] you would be talking about ground motions that are in excess of 2 feet per second, for two minutes or more." 

Theorizing about what would happen if the ground repeatedly and violently rose and fell by 2-plus feet at a time, Bender doesn't mince words: older buildings — specifically anything built before 1970s — would likely collapse. Overpasses and bridges, too. 

All basic utilities would be interrupted — most gas, water, electricity lines that service Southern California cross the San Andreas fault line and would be inaccessible for at least a week, probably more. City sewer systems would be incapacitated for months. Most of this would happen after the first round of shaking, and doesn't account for the additional damage brought on by large aftershocks that will likely follow. 

Locally, cities that sit atop the Santa Ana riverbed — such as Huntington Beach and Fountain Valley — would feel the brunt of the shaking, an unfortunate consequence of being built on soft sedimentary rock that once formed the bottom of one of the region's largest waterways. 

The San Andreas fault — which extends roughly 800 miles across California, beginning just east of San Diego at the Salton Sea and ending off the coast about 250 miles north of San Francisco — last erupted in 1875 with a 7.9 quake that became known as the Fort Tejon Earthquake. That temblor stretched for 225 miles and was so powerful that soil liquefied, causing trees across region to sink. 

The Fort Tejon quake was preceded by several foreshocks a few short hours before the main event, a common occurrence before major earthquakes and the best chance the state has for an early warning before the next Big One. "About half of the really big earthquakes that have occurred throughout history have had foreshocks," Bender says. 

It's this fact that spurred seismologists to issue an earthquake warning in late September after a swarm of earthquakes ruptured near the Salton Sea. 

Even so, Bender urges people to take the warnings with a grain of salt. "Currently, the probability of an earthquake larger than 7.8 occurring along the San Andreas is 1 percent. With the swarm, that probability jumped to 2 percent, but only for about 24 hours." 

It's not an excuse to grow complacent. Historically, the San Andreas has endured a major rupture every 145 years, give or take 15 years. That timeline means that come next year, we'll be overdue. 

"I think of this as a scary time because there seems to be a lull in the amount of earthquakes that are occurring," Bender says. "Twenty years ago we had much more seismic activity, but now all of a sudden, everything's turned off. We're getting to a place where people don't expect it, and reality is it could happen tomorrow. That's a dangerous place to be."