Study: Santa Rosa could see 7.1 quake on Rodgers Creek fault

The Rodgers Creek fault that cuts through the heart of Sonoma County and produced a 4.4 magnitude earthquake and a 4.3 aftershock Tuesday is one of four major faults in the Bay Area primed with enough pent-up energy to produce a major quake — and it’s overdue for a big one, according to a 2016 study.

Scientists reached their conclusions after poring through historical data and taking extensive measurements of “fault creep” across the earthly fissures that define the 44-mile-wide San Andreas fault system.

Fault creep is the slip in the uppermost part of the earth’s crust along a fault line. Stress in the earth’s crust is released with this gradual creeping, diminishing the strain and potential energy of a given fault.

(From 2016: New maps detail wider Rodgers Creek fault through Santa Rosa)

But Rodgers Creek is considered “locked” because it has had hardly any measurable creep and is therefore likely to be “eventful,” said geophysicist James Lienkaemper with the U.S. Geological Survey, a lead author of the 2016 study produced jointly with researchers from San Francisco State University.

Researchers estimate Rodgers Creek, which runs from San Pablo Bay to the northern outskirts of Santa Rosa, has accumulated enough strain to produce a magnitude-7.1 temblor. It is listed with three other fault segments in the Bay Area’s earthquake system that have accumulated significant strain - the Hayward fault between Suisun Bay and San Jose, the Calaveras fault from Hollister to Danville and the Green Valley fault from Vallejo to Fairfield.

“They are loaded for an earthquake the size of which you would expect significant damage,” Lienkaemper said in 2016.

The research adds to a constellation of reports and findings that have put the entire Bay Area on alert for the next big one.

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