After the Ridgecrest earthquake on July 4, Scott Brandenberg and Jonathan Stewart, UCLA professors of civil and environmental engineering, got in a car and drove to the epicenter. Stewart organized a seven-member team of earthquake researchers with the goal of gathering time-sensitive data in Ridgecrest and Trona, California.
They were in a motel when the second, larger 7.1 temblor struck the following day. “I was not very far away from where you check in,” Stewart says. “A young woman, who I recognized from check-in, ran out of her office. ... She was really scared. People in the hotel were running out of their rooms. We reassured everyone as best we could that they were not in danger, [and] there was no need to panic.”
For these motel guests and millions of Californians, the Ridgecrest quakes were a wake-up call to learn more about earthquake safety and policy. To debunk some common myths and misconceptions, we interviewed Brandenberg and Stewart to get the facts and learn how UCLA researchers are “turning disaster into knowledge.”
Myth: During an earthquake, the biggest threat to safety is collapsing buildings.
“During the event, most injuries are from nonstructural components falling — for example, a TV or a cabinet that isn’t tied to a wall,” Stewart says. “And in the aftermath of a large earthquake, far more people would be affected by a loss of water, gas, electricity and cell service. Some buildings will collapse, but there won’t be a lot of them.” Fearing a building collapse, many people immediately run outside, but Stewart cautions against this. “The last place you want to be is right outside a building,” he says. “Things fall off: roof tiles, stucco, air conditioning units. Stay inside, drop, cover and hold on, and leave after the shaking stops.”
Myth: During an earthquake, you should stand underneath a door frame.
This common misconception dates back to the 19th century, when many homes were built with adobe. Adobe structures were prone to crumbling during a large earthquake, leaving only the wooden door frame standing.
Today, this advice is out of date. Standing in a doorway does not protect you from falling objects, and during the event, doors can swing back and forth wildly, potentially hitting you or crushing your fingers. Stewart agrees with the Federal Emergency Management Agency and the U.S. Geological Survey’s advice to drop, cover and hold on:
Myth: My building will be fine. We have codes.
“While we have had codes for decades,” Stewart says, “the reliability in terms of seismic protection of a code from the 1960s and 1970s is not nearly as good as a code in the modern era. We’ve learned a lot about what makes buildings vulnerable.” However, he cautions, many structures built to code in the last 10 years are still damage-prone. “Even with a modern code,” Stewart says, “the intention is that the building won’t kill you, that you would be able to survive the event and walk out of the building. Your person will be fine, but your overall situation might be very much not fine. You may not be able to go back into your home or your business. You may have a complete financial loss. Per the objectives of the code, that is a success.”
UCLA research helps regulators and builders understand seismic demands in different regions and design more resilient structures. “Our research is used in the National Seismic Hazard maps produced by the USGS, which affect the design of almost all structures built in the U.S.”
Myth: California is going to break off into the sea.
“The plate boundary that we have in most of California is the San Andreas, a strike-slip fault,” Stewart says. “The movement across a strike-slip fault is lateral.” In other words, there are two plates sliding past each other, but they will not move apart from one another. “There’s no elevation loss that would cause land to fall into the sea,” he adds. Even if we look north of Mendocino [California], into Oregon and Washington, where large subduction earthquakes occur, we typically find after large subduction earthquakes that the ground surface in coastal areas rises, not descends. Nowhere along the West Coast of the United States is ‘falling into the sea’ a problem.”
Myth: The government will take care of us in the aftermath.
“In the event of a major earthquake in Los Angeles, there is the potential for disruption to many services we rely on on a daily basis, including water, electricity and cellular service,” Stewart says. “After a major earthquake, there will be a period of time — one to two weeks — when you’ll be on your own. Make a plan in advance for you and your family so you’re prepared until the government has time to deliver aid.” For more information on earthquake safety and preparedness, visit ready.gov.
Myth: The ShakeAlert app didn’t go off during the Ridgecrest earthquakes. It must be broken.
L.A.’s ShakeAlert app triggers alerts based on the intensity of shaking, not magnitude. The epicenters of the July earthquakes were far from Los Angeles, so shaking was not intense enough to trigger alerts in the greater Los Angeles area.
Officials are aware of the public reaction after the July temblors. “Because the lack of an alert caused some people to falsely assume that the system doesn’t work, [officials] have revised it so that a large magnitude earthquake that produces small shaking will nonetheless trigger an alert,” Stewart says. “That’s not needed for safety reasons; it’s just to help the public have more confidence in the app.”
Myth: The chances of the big one happening are low.
The risk of a large earthquake on the San Andreas fault is actually quite high. “The San Andreas fault produces large earthquakes on an average time interval of every 150 to 200 years or so,” Stewart says. “There are portions of the San Andreas, including near San Bernardino, that have not had an earthquake in over 300 years. In short, we’re overdue.”
Myth: The only earthquakes that can threaten L.A. are actually in L.A.
Earthquakes hundreds of miles away can have a major impact on Los Angeles. For example, about 40 percent of our water supply is vulnerable to a significant earthquake in Northern California. According to Brandenberg, “The Sacramento–San Joaquin River Delta is the hub of the state’s water distribution system, delivering fresh water to more than 25 million residents and 3 million acres of farmland. Delta water conveyed through a network of levees is crucial to Southern California. … Had [2014’s] magnitude 6.0 Napa earthquake been located a few miles to the southeast, it could have caused a severe shortage of fresh water.”
Stewart adds, “This is something that UCLA researchers are deeply involved in, especially understanding the nature of seismic risk in the Delta. Our work has addressed both the demand assessment [how strong the shaking would be] and the performance evaluation [how the levees would likely deform]. This information is highly relevant to the Department of Water Resources, which manages this critical infrastructure.”
Myth: We can predict earthquakes.
“We’re used to weather forecasts for tomorrow or a week from now,” Stewart says. “We can’t predict earthquakes on those kinds of time horizons. What we can do is predict them on long time horizons that are more akin to the geologic cycles. We can predict probabilities of earthquakes and shaking levels over the next 50 years or 100 years, and we can do that fairly well. UCLA is involved in producing the models used to predict ground shaking levels in future earthquakes, which is a critical element in our building codes.”
After the Ridgecrest quakes, Stewart’s goal was to gather data and release a report within two weeks. “The details of the fault rupture are slowly being lost,” Stewart says. “Data is lost through cleanup efforts and natural processes. In Ridgecrest, there’s earthquake tourism — people walking around the fault. And there’s natural processes. ... It’s a very hot and dry and windy area.”
Working against the clock, the team fanned out across the area to collect observations. “We looked for fault displacement, landslides, liquefaction and ground deformations that are produced by liquefaction. We looked for how different types of structures performed, and how that relates to the soil conditions beneath them. We have evaluated the intensity of ground shaking from recording instruments.” Stewart’s team released their Ridgecrest report on July 19. This data helps grow our knowledge of earthquakes, and it will be useful in future research to improve public safety and provide more reliable seismic risk assessments in California and around the world.