The faults beneath Southern California are wound tighter than they have been in a millennium. A new study finds that tectonic stress on the San Andreas and San Jacinto fault systems has reached, and in places exceeded, the highest levels seen in the past 1,000 years, leaving the region in what researchers call a critically loaded state.
To be clear about what this is and isn’t: scientists are not predicting a date for the Big One. They are reading a pressure gauge, and the needle is in the red.
What the study found
The research, published June 3 in the Journal of Geophysical Research: Solid Earth, was led by Liliane Burkhard of the University of Bern and the University of Hawaii. Her team built a physics-based earthquake cycle model and fed it 1,000 years of seismic history reconstructed from radiocarbon dating, tree-ring anomalies and historical records of ground ruptures, then used it to estimate present-day stress.
The numbers are stark. The San Jacinto-Bernardino section is now carrying about 3.6 megapascals of stress, exceeding the highest value seen anywhere in the entire 1,000-year simulation, while the neighboring Mojave South section of the San Andreas sits at 2.8 megapascals…