SAN BERNARDINO, Calif., June 24 (Inland Empire News Online) — A peer-reviewed study led by University of Hawaiʻi at Mānoa earth scientists says 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 1,000 years.
The finding has direct relevance for the Inland Empire, where the study points to San Bernardino, Riverside and Cajon Pass as part of a corridor that could be affected by a major earthquake. The research was published in the Journal of Geophysical Research: Solid Earth.
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 stress levels across 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 a University of Hawaiʻi at Mānoa release.
The study says that kind of joint rupture could be more damaging than a quake on one fault alone. The release said it could affect densely populated areas including Los Angeles, San Bernardino, Riverside and the Coachella Valley.
Burkhard said the fault system is under unusually high load.
“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,” she said.
The study focused on the San Andreas and San Jacinto fault systems, two of the most closely watched earthquake sources in Southern California. The research team said the present-day stress pattern is important for seismic hazard assessments in a region where millions of people live and where roads, utilities and other infrastructure cross the faults.
The study modeled stress at 3.6 MPa on the San Jacinto-Bernardino section, which the Phys.org summary said was higher than any value in the 1,000-year simulation. It also put stress at 2.8 MPa on the nearby Mojave South section of the San Andreas Fault.
According to the University of Hawaiʻi at Mānoa release, Cajon Pass is a key area because it could help a rupture move through both fault systems at once. The release said that kind of through-going event would be significantly more damaging than a single-fault earthquake.
The UH release did not give a date for the last major rupture it referenced, and the source material provided for this report did not include the full journal paper, its methods or its uncertainty bounds. The study was led by scientists at UH Mānoa and published in the peer-reviewed Journal of Geophysical Research: Solid Earth.
