SAN BERNARDINO, Calif., June 24 (Inland Empire News Online) — A University of Hawaiʻi at Mānoa-led study published in the peer-reviewed Journal of Geophysical Research: Solid Earth says tectonic stress along Southern California’s San Andreas and San Jacinto fault systems has reached, and in some places exceeded, the highest levels seen in the past 1,000 years.
The research was led by Earth scientists at UH Mānoa, with lead author Liliane Burkhard, a research affiliate in the Hawaiʻi Institute of Geophysics and Planetology at the university’s School of Ocean and Earth Science and Technology and a scientist at the University of Bern in Switzerland.
The University of Hawaiʻi said the results have direct implications for seismic hazard assessments in a densely populated and infrastructure-critical corridor in Southern California.
According to the study, modeled stress reached 3.6 megapascals on the San Jacinto-Bernardino section, the highest value seen anywhere in the 1,000-year reconstruction, and 2.8 megapascals on the neighboring Mojave South section of the San Andreas Fault.
The university’s release said the study points to Cajon Pass as a place that could help a joint rupture of the two fault systems occur at the same time.
The release said a through-going rupture involving both faults could be significantly more damaging than a single-fault event. It said the scenario would affect densely populated parts of Southern California, including Los Angeles, San Bernardino, Riverside and the Coachella Valley.
“Our results show that stress levels on multiple fault segments are now at or above the highest values seen in the past millennium and that the region may be capable of a large through-going rupture involving both fault systems,” Burkhard said in the university release.
Burkhard also said, “Right now, with stress at historically high levels across the region and more than 160 years elapsed since the last major rupture, the system is in a critically loaded state.”
The release did not identify the last major rupture by name, date or location, and it did not provide the study’s full methods, sample size or uncertainty bounds around the 1,000-year stress reconstruction. It identified the article as peer reviewed and published in Journal of Geophysical Research: Solid Earth.
The university said the findings matter because the San Andreas and San Jacinto systems cut through heavily populated inland and coastal parts of Southern California, with the study highlighting San Bernardino County, Riverside County and the broader Inland Empire corridor as part of the area that could be affected by a large rupture.
