A new scientific warning has put California’s earthquake risk in sharp focus: supershear earthquakes—rare, high-speed ruptures that outpace traditional seismic waves—pose a growing threat to the state’s most populous regions. As researchers predict multiple magnitude 7 or greater quakes in the coming decades, the question looms: is California ready for the next seismic shock?
Supershear: The Fast-Moving Threat
Recent studies reveal that over a third of large strike-slip earthquakes worldwide in the past 15 years have exhibited supershear characteristics—meaning their ruptures raced ahead of standard seismic waves, amplifying ground shaking and damage. California’s long, straight faults, such as the San Andreas, are especially prone to this phenomenon. The 1906 San Francisco earthquake, for example, is now believed to have been a supershear event, according to a 2008 analysis.
Supershear earthquakes unleash a “double strike”: an initial shock front followed by trailing waves, extending intense shaking over a wider area and for a longer duration than typical quakes. This can trigger secondary hazards like landslides and fires, compounding the risk for millions living near active faults.
Mounting Pressure Along California’s Faults
California’s seismic landscape is defined by its mature, locked faults—especially the San Andreas, which has not experienced a major rupture in over a century. This prolonged inactivity has allowed enormous stress to build up underground. “The longer the fault remains locked, the greater the stored energy, which can potentially result in more destructive rupture dynamics when it is released,” explained Dr. Yehuda Ben-Zion, lead author of a recent study from USC Dornsife College and the Statewide California Earthquake Center.
On September 19, 2025, Ben-Zion and colleagues published findings in *Seismological Research Letters* warning that “over the next few decades, we will have multiple magnitude 7 earthquakes in California. They are coming, whether we are prepared or not.” The researchers urge immediate updates to building codes and seismic monitoring systems to address the unique dangers of supershear events.
Urban Vulnerability and Local Voices
With about 70% of California’s population living within 30 miles of an active fault, the stakes are high for cities like Los Angeles, San Francisco, and communities such as Coachella and Palo Alto. Many residents recall the devastation of past quakes and worry that current building standards may not be enough.
“We’re sitting right on top of the fault, and a lot of our older homes just aren’t built for this kind of shaking,” said an Indio city council member. “We need to make sure our most vulnerable neighbors are protected before the next big one hits.”
Critical infrastructure—hospitals, schools, and utilities—could face widespread disruption if a supershear quake strikes a densely populated area. Vulnerable populations in older housing stock are at particular risk if building codes remain unchanged.
Debate Over Preparedness and Policy
The scientific community is divided over how best to prepare. Some seismologists argue that limited resources should focus on retrofitting the most vulnerable structures, regardless of quake type. “Supershear events are a concern, but the priority should be strengthening what we already know is at risk,” Lay said.
Others, including Ahmed Elbanna, incoming director of the Statewide California Earthquake Center, advocate for integrating supershear scenarios into hazard maps and building codes. Elbanna is leading efforts to model these events and push for policy changes, signaling a shift toward advanced research and community engagement.
California’s ShakeAlert early warning system is expanding, with over 1,500 seismic stations now operational and a goal of 1,675 by 2025. The state has also allocated more than $20 million for seismic retrofit grants, extending eligibility to rental properties for the first time.
Global Lessons and Legal Stakes
Supershear earthquakes have caused catastrophic damage elsewhere. In February 2023, two supershear quakes in Turkey and Syria killed at least 58,000 people, underscoring the potential for devastation in urbanized regions. Both California’s San Andreas and Turkey’s East Anatolian faults share the structural traits that enable supershear ruptures.
Internationally, California collaborates with Japan and Turkey on earthquake preparedness, sharing research and best practices for managing supershear risks. Legal frameworks in California hold property owners and developers liable if structures fail to meet seismic standards, and recent expansions of retrofit grant programs reflect a growing recognition of both legal and ethical responsibilities.
Looking Ahead: Building Resilience
Public awareness is rising through initiatives like the Great California ShakeOut, which engaged over 10 million participants in 2024, and new educational programs targeting students. Yet, as the debate over building code updates continues—balancing seismic safety with housing affordability—the challenge remains to translate scientific warnings into effective action.
Supershear research is reshaping California’s understanding of earthquake risk, but the core message is clear: comprehensive seismic upgrades and robust preparedness are essential to protect millions from potentially catastrophic damage, whether the next major quake is supershear or not.