SAN BERNARDINO, Calif., June 24 (Inland Empire News Online) — A University of Hawaiʻi at Mānoa-led study published in a peer-reviewed journal says tectonic stress on the San Andreas and San Jacinto fault systems in Southern California has reached, and in some places exceeded, the highest levels seen in the past 1,000 years, sharpening concern for the Inland Empire and nearby regions.
The research appeared in Journal of Geophysical Research: Solid Earth and was led by Earth scientists at UH Mānoa, according to a university news release. Lead author Liliane Burkhard is a research affiliate in the Hawaiʻi Institute of Geophysics and Planetology at the UH Mānoa School of Ocean and Earth Science and Technology and a scientist at the University of Bern in Switzerland.
The university said the study has direct implications for seismic hazard assessments in a densely populated corridor that includes San Bernardino and Riverside counties and wider Southern California. The release said the fault system is in a critically loaded state and that more than 160 years have passed since the last major rupture.
“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 release.
That finding matters most for communities in and around the Inland Empire, where the San Andreas and San Jacinto systems run through a landscape packed with homes, roads, rail lines and other infrastructure. The university release said a possible joint rupture could be significantly more damaging than a single-fault event.
The release identified Cajon Pass as a place that could help one rupture spread across both fault systems. It said such a scenario could affect Los Angeles, San Bernardino, Riverside and the Coachella Valley.
The study does not describe a forecast of when a large earthquake will happen, but it does place the region in what the authors describe as a high-stress state based on their reconstruction of fault loading over the past millennium. The journal publication means the work has passed peer review.
The university release said the researchers compared current tectonic stress against the highest levels seen over the past 1,000 years. It framed the result as a warning sign for seismic hazard planning along one of California’s most heavily populated earthquake corridors.
The study’s main conclusion is centered on the fault system as a whole, rather than on a single isolated section. That makes the Inland Empire part of the core risk area highlighted by the authors, especially where the two fault systems come close together near Cajon Pass.
