San Andreas Fault reaches highest stress level in 1,000 years

University of Hawai’i researchers reported that the San Andreas Fault has reached its highest stress level in 1,000 years. The 750-mile fault has not produced a major earthquake since the 7.9-magnitude Fort Tejon event in 1857. It last produced a large quake on Christmas Day 1899.

” Researchers used 1,000 years of earthquake records, tree-ring data, and sediment dating to run physics-based simulations. The models indicate stress on multiple segments now equals or exceeds the highest values recorded in the past millennium. The same simulations show the Cajon Pass could act as an earthquake gate, sometimes blocking and sometimes allowing a rupture to cross between the two faults.

Potential consequences A simultaneous rupture of both faults could affect Los Angeles, San Bernardino, Riverside, and the Coachella Valley. The researchers said the findings support emergency planning and infrastructure assessments but cannot predict when an earthquake will occur.

California officials have previously stated there is at least a 50 percent chance of one or more magnitude-7.0 or larger quakes in the region in coming decades.