The California Quake That Could Reshape America
California’s next major earthquake may not stay on a single fault. New research is revealing how stress at one of Southern California’s most important fault junctions could influence whether a future rupture stops—or spreads into a much larger event.
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Deep beneath Cajon Pass, the San Andreas and San Jacinto fault systems come dangerously close together. New 2026 research reconstructed roughly 1,000 years of earthquake history and modeled how stress has evolved across this complicated junction. One San Jacinto segment reached an estimated 3.6 MPa of Coulomb stress by 2025, while simulations suggest changing stress relationships could influence whether separate fault segments rupture together.
But this is not an earthquake prediction.
The bigger discovery is that Cajon Pass may behave like an “earthquake gate.” Under some conditions, its complicated geometry could stop a rupture. Under others, stress conditions may allow an earthquake to continue through multiple major fault segments.
In this DiscoverTube investigation, we explore the San Andreas Fault, San Jacinto Fault, Cajon Pass, earthquake stress accumulation, GPS deformation, cascading rupture scenarios, and what scientists are learning about the possibility of a much larger Southern California earthquake.
Could one earthquake jump from one fault system to another?
And if a major rupture begins near this junction, will Cajon Pass stop it—or become the gateway to something much bigger?
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In this video:
• The San Andreas–San Jacinto fault junction
• 1,000 years of reconstructed earthquake history
• Stress building around Cajon Pass
• The segment modeled at 3.6 MPa
• Why Cajon Pass could act as an “earthquake gate”
• How fault geometry can stop major ruptures
• The 1992 Landers earthquake and stress transfer
• Potential cascading earthquake scenarios
• San Jacinto Fault seismic activity
• Earthquakes reaching 22 kilometers underground
• The Cajon Pass scientific drill hole
• GPS measurements of Southern California deformation
• Why earthquake stress does NOT provide a countdown
• The infrastructure exposed around Cajon Pass
• What could determine the size of California’s next major rupture
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References:
“Cajon Pass and the Southern San Andreas Fault System: Earthquake Cycle Stress Accumulation and Present-Day Loading”, via USGS / JGR Solid Earth
https://doi.org/10.1029/2025JB033213
“Stress States on the Eve of Past Earthquakes Inform Earthquake Rupture Through Fault Complexity Along the San Andreas and San Jacinto Faults”, via USGS / Bulletin of the Seismological Society of America
https://doi.org/10.1785/0120250173
“Change in Failure Stress on the Southern San Andreas Fault System Caused by the 1992 Magnitude 7.4 Landers Earthquake”, via USGS / Science
https://doi.org/10.1126/science.258.5086.1328
“Static Stress Changes and the Triggering of Earthquakes”, via USGS / Bulletin of the Seismological Society of America
https://doi.org/10.1785/BSSA0840030935
“New Evidence on the State of Stress of the San Andreas Fault System”, via USGS / Science
https://doi.org/10.1126/science.238.4830.1105
“Predicted Variation of Stress Orientation With Depth Near an Active Fault: Application to the Cajon Pass Scientific Drillhole, Southern California”, via USGS / Geophysical Research Letters
https://doi.org/10.1029/GL015i009p01009
“Hydraulic Fracturing In Situ Stress Measurements to 2.1 km Depth at Cajon Pass, California”, via USGS / Geophysical Research Letters
https://doi.org/10.1029/GL015i009p01005
“Cajon Pass and the Southern San Andreas Fault System”, via Statewide California Earthquake Center
https://central.scec.org/publication/15025
“Stress States on the Eve of Past Earthquakes”, via Statewide California Earthquake Center
https://central.scec.org/publication/13437
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