SAN BERNARDINO, Calif., June 24 (Inland Empire News Online) — A peer-reviewed University of Hawaiʻi at Mānoa study says tectonic stress along 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, a finding with direct implications for earthquake hazard in the Inland Empire and across the region.
The research was published in the Journal of Geophysical Research: Solid Earth, meaning the work has passed journal review, and it was led by Earth scientists at UH Mānoa. The university said the study focuses on a fault network that runs through one of the nation’s most populous and infrastructure-critical corridors.
According to the study, modeled stress reached 3.6 MPa on the San Jacinto-Bernardino section, the highest level seen anywhere in the 1,000-year simulation, and 2.8 MPa on the neighboring Mojave South section of the San Andreas Fault.
Lead author Liliane Burkhard, 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, said the results show multiple fault segments are now at or above the highest values seen in the past millennium.
“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.
The study also points to Cajon Pass as a place that could help a joint rupture move across both fault systems at once. The university said such an event could be significantly more damaging than a rupture on a single fault.
That potential matters for the Inland Empire because the study and the university release identify San Bernardino and Riverside as among the areas that could be affected, along with Los Angeles and the Coachella Valley.
“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,” Burkhard said.
The research frames the finding as a seismic hazard issue rather than a timing prediction. The university release said the results have direct implications for hazard assessments in Southern California, but it did not provide the study’s full model details or uncertainty bounds in the material reviewed.
The author list and affiliations in the university release identify Burkhard as a research affiliate in the Hawaiʻi Institute of Geophysics and Planetology at UH Mānoa and as a scientist at the University of Bern. The university said the work adds new evidence for how stress is building across the San Andreas and San Jacinto systems in Southern California.
