Study Finds California Fault Stresses at Highest Levels in a Millennium
Research published in the Journal of Geophysical Research indicates that tectonic stresses in Southern California have risen to their highest levels in 1,000 years, raising concerns about the potential for a large multi-fault earthquake.
A new study published in the Journal of Geophysical Research reports that accumulated tectonic stresses in Southern California are higher today than at any point in the past millennium. The research, conducted by an international team led by University of Bern earth-science researcher Liliane Burkhard, modeled 1,000 years of earthquake activity along the San Andreas and San Jacinto fault systems.
The model shows that stress has been building since the 1857 magnitude 7.9 earthquake, now reaching or exceeding levels recorded over the last 1,000 years. Burkhard explained that the simulation tracks how each quake alters stress on neighboring fault segments, how stress accumulates during quiet periods, and how deeper crustal layers relax after large ruptures.
The team identified the Cajon Pass as a critical fault junction, describing it as an "earthquake gate" that can either limit seismic activity to a single fault or allow it to propagate across both faults. Historical events in 1857 and 1812 are cited as examples of these two scenarios.
"The question of when and how the next major earthquake will occur in this region is one of the most pressing problems in applied geoscience," Burkhard said.
The researchers caution that while the study does not predict the timing of a future quake, it provides a physics-based assessment of current stress conditions and a framework that could be applied to other complex fault junctions worldwide.