A new study of Southern California’s major fault systems has found that tectonic stress is now at its highest level in at least 1 000 years, raising new questions about how future large earthquakes could unfold near Los Angeles.
Researchers modeled 1 000 years of earthquake history along the San Andreas Fault and San Jacinto Fault and found that stress has continued to build since the last major rupture to affect the wider Los Angeles region — the M7.9 Fort Tejon earthquake in 1857.
Their results suggest that a key fault junction known as Cajon Pass may play a critical role in determining whether a future earthquake remains on a single fault or spreads across multiple fault systems.
The study, led by Liliane M. L. Burkhard of the University of Bern and published in the Journal of Geophysical Research: Solid Earth, introduces the concept of Cajon Pass as an “earthquake gate” — a fault junction that can either stop a rupture or allow it to continue into neighboring faults under the right stress conditions…