Shaking out the facts

David Oglesby tells whether the ‘big one’ is in La Verne’s immediate future

by Celene Vargas
photography by Jolene Nacapuy

David Oglesby, department chair of Earth sciences and professor of geophysics at the University of California Riverside, explains that when scientists understand exactly how strong the rocks are on a fault and how much friction they exert, then they might be able to come close to predicting earthquake activity. Faults are locked by friction, and the plates move at a constant rate. At some point in time, when the plates no longer can hold back the friction, they slide and cause an earthquake. / photo by Jolene Nacapuy

“I remember everything started shaking,” says Katrina Sire, adjunct faculty for the office of community engagement and the writing program, recalling her first earthquake experience, the Whittier Narrows 5.9 magnitude shaker that struck at 7:42 a.m. on Oct. 1, 1987. Prior to this moment, she didn’t even know what an earthquake was. “I was about 9 years old, and we were getting ready for school. I just dropped my backpack and ran to the nearest doorway to hide. My sister’s bedroom was at the front of the house, and it hit harder there for some reason. She ran out of her room into the hallway, and the radiator’s grill fell on her. It was terrifying; I won’t ever forget the earthquake. My neighborhood actually set up tents outside, and everyone slept in their front yards for a couple nights because everyone was saying there was going to be a big one afterward.”

Despite this harrowing account, the “big one” has not happened yet, but we are due for one, says David Oglesby, department chair of Earth sciences and professor of geophysics at the University of California, Riverside. “Everyone in California should wake up ready to face an earthquake.” Earthquakes in California are long feared but sometimes reduced to a source of entertainment in parody videos like one recently released by Buzzfeed, which shows how people from Los Angeles are more surprised by rain than by earthquakes. In the video, workers at an office panic when it starts to rain. At the end, once it stops raining, an earthquake hits, and two Californians react flippantly, only sparing a moment’s thought before laughing and going back to work. People may see quakes as a laughing matter because they are not aware of the dangers they are facing. Also, there has not been a “major” quake in California since 1857.

La Verne’s quake threat

The threat is local with the city of La Verne having two major fault lines that pose a danger: the San Andreas fault and the Sierra Madre fault. “It’s already known that La Verne is at a high seismic risk,” says David, who grew up in Claremont, California. He says La Verne residents should be more cautious of the Sierra Madre fault. “The San Andreas [fault] certainly does pose a danger to La Verne, but even closer than the San Andreas, the biggest fault is the Sierra Madre fault zone. It underlies the San Gabriel Mountains. That’s why the San Gabriel Mountains are there; they’re being lifted up on the Sierra Madre fault.” Most at risk, says the scientist, are big ranch style homes that are popular in California and are seen in certain parts of La Verne and surrounding areas. They pose more of a safety risk than standard one-story houses. “The one story homes are relatively strong and not brittle so they tend to hold up well during earthquakes.” However, during an earthquake, the real danger does not come from a building collapsing on people. “Drop, cover and hold on is what you want to do because, in an earthquake, the real danger for most people in California is stuff in the building falling on you,” he says. If there is no desk or sturdy chair to hide under, the next best thing is to stay against a wall that does not have anything mounted on it. David stresses to avoid running outside. However, if a person is already outside when an earthquake hits, it is best to stay there.

Myths about how to survive earthquakes have circulated, like camping outside the way Katrina’s neighbors did following the Whittier event. David remembers reading an email chain myth called “The Triangle of Life,” telling people not to hide under desks but to crouch next to them. That way, if something were to fall on the desk, it would create a triangle shielding the person from any more danger. The person giving the information claimed to be an expert in earthquakes when he actually was not. “This kind of information that gets circulated is dangerous. You should always double check the sources,” he says.

Earthquake dangers

In order to combat the dangers posed by these fault lines, California has earthquakes codes that dictate how structures should be built so they are resistant to seismic activity. Despite this, some buildings have not been retrofitted, and one enters at her own risk. Plaques on some D Street Old Town shops used to warn shoppers that a few buildings were not up to earthquake codes. David says that luck is also involved in a building surviving a major quake. He notes that some buildings will be intact while others are knocked down because of the soil composition. Structures built on bedrock tend to do better than those erected on sediment, which tends to “liquefy” during major quake activity.

Earthquakes become a real issue when they cross the “five” on the seismic scale. “Quakes higher than five could start causing significant damage. You start getting into the sixes, and you run the risk of fatalities. Higher than that, and you start running into major disaster territory,” David says. Scientists have determined that when the San Andreas last broke, it registered a 7.9 in 1857 in Fort Tejon—a high number but hardly the mammoth quake modeled in the movie “San Andreas.” This popular 2015 release shows massive tsunamis and the ground breaking apart. In order for tsunamis to happen, the San Andreas Fault would have to be a thrust fault, meaning the fault plates would overlap each other at an angle so when they move, the ground would be pushed up. It would also have to be near water. In reality, the San Andreas is a strike-slip fault that has two plates sliding past each other. There is no pulling apart, and the ground does not get pushed up; it just causes it to shake. Also, the San Andreas fault is on the other side of the San Gabriel Mountains. The closest it comes to La Verne is near Wrightwood, which David says is not close enough to the ocean for a tsunami to develop. “Even the largest conceivable earthquake happening in California will not break off a chunk of California and turn it into an island or sink it into the ocean. The sense of fault motion property is wrong even if you ignore the matter of scale.” In other words, there will be no beach-front property in Arizona. However, the Sierra Madre fault is a thrust fault and can cause mountain rockslides, but La Verne residents in the valley do not have to worry about giant boulders falling on them.

Predicting earthquakes

The San Andreas fault line does not have the predictability of the Old Faithful Geyser in Yellowstone National Park, but it has slipped a few times in recorded history, and many people try to chart its frequency to predict when it may break again. “The timing is not consistent in general,” David says. “When you look at the historical, even prehistorical geological record of earthquakes, you rarely find anything that looks regular.” While scientists cannot predict when an earthquake will happen, they can look to the past. “In nature, we know that if it has happened before, it can happen again.” This is the kind of work David does. He and his team create simulations using examples from past earthquakes to see how future shakers can affect Southern California. The data they collect from the simulations can then be used for city plans and guide new building construction.

Even though there has not been a modern era earthquake in Southern California with a magnitude of 7.9, it is true residents are due for one. “It is a waiting game,” David says. “Now, as a scientist and public safety enthusiast, I vote that we don’t wait. There is a lot we can do in the meantime to prepare ourselves for it, but we can’t do anything about the earthquake itself; it will happen.” Many people, whipped into an earthquake frenzy by the media, think this means the next big quake will tear the ground from the desert to the Central Valley. David says that is not the case. “To have an earthquake of a certain size, you have to have a fault of a certain size, and while the San Andreas is big, but it isn’t that big. The great Chilean earthquake of 1960 was magnitude 9.5. It had numerous aftershocks the size of the San Francisco earthquake; yet, you didn’t see buildings collapsing like dominoes or giant chasms opening in the ground. There was a tsunami, but it wasn’t hundreds of meters high like something you see in the movie. Everything [in the movie] is not just turned up to 11 but to 25 on a scale of 10.”

So what kind of damage can a 7.9 earthquake cause? The Fort Tejon earthquake of 1857 caused trees to be uprooted and buildings to be destroyed. Strong shaking happened that lasted up to three minutes. It was felt in San Diego and Las Vegas; there were two fatalities, one being a heart attack. Foreshocks were reported up to nine hours before the main quake. However, David says not even foreshocks can be a reliable pre-indicator. “Nature doesn’t care what we call them; they’re all earthquakes.” He says seismographs don’t indicate whether an earthquake is a foreshock, main shock or aftershock. Every once in a while, what scientists believed to be an aftershock is stronger than the main earthquake. The closest scientists have come to predicting an earthquake is by placing sensors near fault lines. This only gives a few seconds of notice, but it can be enough to at least turn off utilities. David says that sensors on the San Andreas fault could give up to 20 seconds notice to prepare if the signal is sent to Los Angeles. However, placing the sensor on the Sierra Madre fault line would not be as helpful, given its proximity to La Verne. And while the sensors are utilized in Japan, they are still going through a trial period before installation in California.

How to prepare for a disaster

The best thing to do is to be prepared. David suggests buying multiple emergency bags, at least one for the house and one for the car. He did it himself this year, buying a basic kit from Lowell’s. The bags should have food and water that can last for a few days in case one is trapped. If a person cannot get out from where she took cover, chances are no one else will be able to perform a rescue immediately. David references Hurricane Katrina and how it took days for people to receive aid. He also suggests bolting things down, like bookcases, and not having heavy objects above the bed, like paintings or frames. He tells the story of a student who slept through an earthquake only to awake in the morning with a huge TV that flopped off its wall mount onto the bed right next to his head. He stresses to never run outside during an earthquake and recalls the story of two women who ran outside of a shop during a California quake in the early 2000s and died because roofing materials fell on them. Everyone who stayed inside was fine.

As a scientist with extensive earthquake knowledge, David says he tries not to always think about pending danger, but sometimes he will observe a building’s structural integrity. “I was house hunting and found a house with large windows, which already make me nervous, but the house was also on a cliff with the back being held up by stilts.” Even some of the UC Riverside buildings make him nervous, he says, especially the ones with all glass. Fortunately, he knows that those buildings are reinforced with steel. “There is safety in knowing that even if a destructive earthquake were to hit Southern California, it won’t cause as many fatalities as it would in a less developed country. I don’t want to scare people; I just want them to be prepared.”

Essential items when preparing for a disaster include a whistle, local maps, a three-day supply of non-perishable foods and extra batteries. Also handy items to have ready for use include personal sanitation items like hand sanitizer, lotion, maxi pads and Q-Tips. / photo by Jolene Nacapuy