Seismic Science

The largest earthquake to jolt Southern California occurred more than 150 years ago. The Great Fort Tejon Earthquake of 1857 — the biggest recorded quake in state history at magnitude 7.9 — originated in Monterey County, rumbling 225 miles along the San Andreas fault, kicking up dust all the way down to the Cajon Pass north of San Bernardino.

According to reports, the current of the mighty Kern River turned upstream and gushed 4 feet over its banks. The Los Angeles River was also reportedly thrust from its bed. Two people were killed by the temblor, a testament to how sparsely populated the state was at the time.

Studies have shown that it is only a matter of time before another “big one” hits. The chance of having one or more magnitude 7.5 or larger earthquakes in California over the next 30 years is greater than 50 percent. The probability of a smaller, but still substantial, 6.7 magnitude quake occurring in that time period jumps to 99 percent. Let that soak in. With the high-density populations of cities like Los Angeles and San Francisco, a large earthquake could severely damage crucial water aqueducts and power lines, requiring repairs in the billions of dollars. Not to mention the lives that it would jeopardize.

“Earthquakes have become much more disruptive to society than they used to be,” said Thomas Jordan, director of the Southern California Earthquake Center (SCEC), which is headquartered at USC Dornsife. “Our exposure to hazards is much higher, so the risks are higher. That just means we have to understand on the system level what’s going to happen in an earthquake — not just what’s going to happen to my house and what’s going to happen to USC, but what’s going to happen everywhere.”

Thankfully, SCEC, which is funded by the National Science Foundation and U.S. Geological Survey (USGS), is at the forefront of earthquake system science. The science and technology center brings together a network of more than 1,000 earthquake researchers from across the United States and the world to get to the bottom of how exactly earthquakes work and to offer models for forecasting when and where large temblors might occur.

Among the many projects headed by SCEC is an innovative model for forecasting earthquakes called the Uniform California Earthquake Rupture Forecast (UCERF), developed in concert with USGS and the California Geological Survey. UCERF represents the most authoritative estimates of the magnitude, location and likelihood of earthquakes in California, both in the long term and in the short term.

To make these forecasts, hundreds of scientists have contributed their research to create a community earthquake fault model that identifies the myriad faults across the Golden State where the ground has the potential to slip and tremble.

“Geologists have spent decades sweating in the field to map these faults and understand their three-dimensional structure,” said Jordan, University Professor, William M. Keck Foundation Chair in Geological Sciences and professor of earth sciences.

Researchers then use supercomputers to analyze that data and create models to approximate how those faults might break as well as the resulting strong shaking.

The operation is elaborate. Scientists from across institutions and disciplines such as geology, seismology and geodesy — the branch of science that studies the earth’s shape and movement — coordinate their findings into usable seismic hazard estimates. That information guides structure engineering and design and emergency preparedness, as well as insurance premium assessments.

“This research is visionary because this notion of putting it all together and actually creating models that do all of this together is pretty new,” Jordan said. “We don’t really have this type of system-level modeling capability in many places, and so we’ve been trying to develop how that works.”

Other countries are taking notice of how SCEC researchers are collaborating on these grand-scale projects. For instance, scientists in New Zealand recently launched the QuakeCoRE Centre for Earthquake Resilience to connect research programs across national and international institutions. Jordan presented the distinguished lecture on earthquake system science in California at QuakeCoRE’s inaugural annual meeting in 2016. Recently, Jordan met with researchers in China who are working to establish a SCEC-style research center, too. “We are setting a template for how you do this kind of research worldwide,” he said.

The center also has a significant education component that touches all levels of learners. Undergraduates can intern with SCEC while K–12 students can join the citizen-science Quake Catcher Network, in which volunteers place earthquake monitoring sensors in their classrooms or homes to collect seismic data. Students learn about earthquake science from a curriculum that complements gathering the data.

But nothing might be as far reaching as SCEC’s communication and outreach arm as exemplified by the Great ShakeOut Earthquake Drills. SCEC coordinates the annual global disaster preparedness event, which helps individuals and organizations around the world get ready for a major earthquake.

“It’s a remarkable public outreach and educational activity that has taken on significance worldwide, and it’s done right here at USC,” Jordan said.

In 2016, more than 50 million people from more than 70 countries registered to participate in the Great ShakeOut,  which called for participants to practice the “drop, cover, and hold on” drill for at least one minute wherever they were — school, work, home or elsewhere. Some went further, holding table-top exercises, tsunami and fire evacuation drills, safety equipment demonstrations, and even mock search-and-rescue activities.

“The mission of ShakeOut is that everyone, everywhere, should know how to protect themselves during an earthquake,” said SCEC Associate Director Mark Benthien, who coordinates the ShakeOut drills worldwide.

In the decade and a half that Jordan has directed SCEC, he has seen the center directly impact the way scientists understand earthquakes and how the public has learned to prepare for a tremor with the new models and simulations produced to the global preparedness drills run by the center.

“We’ve really changed the way people deal in a practical sense with seismic hazards,” Jordan said.

Read more stories from USC Dornsife Magazine’s Spring/Summer 2017 issue