Researchers say the Rodgers Creek Fault in Northern California, which runs from the San Pablo Bay north through central Sonoma County, could well become the source of the state’s next major earthquake.
The San Francisco Chronicle says the fault is a main strand along the boundary between the North American and Pacific tectonic plates, which rub against each other as they creep in opposing directions.
A magnitude 4.4 earthquake hit Santa Rosa at 6:39 p.m. Tuesday, followed by a magnitude 4.3 aftershock one minute later. They knocked picture frames off walls, cracked water pipes and rattled nerves.
The U.S. Geological Survey pinned the epicenter on a portion of the Rodgers Creek Fault in northeastern Santa Rosa.
The Rodgers Creek Fault is the northern spur of a fault that ends in the hills north of Healdsburg and extends southeastward through central Santa Rosa and under the San Pablo Bay, where it becomes the better-known Hayward Fault that runs under the urban East Bay and had a major rupture in 1868.
Scientists estimate that these connected faults have a 33% probability of experiencing a major earthquake of magnitude 6.7 or higher before 2043. Made by a group of scientists with the USGS, the Southern California Earthquake Center and the California Geological Survey, this forecast put these faults as the most likely sources of the area’s next devastating earthquake.
The Rodgers Creek Fault is a right-lateral strike-slip fault, scientific terms meaning vertical fractures in the Earth’s crust where the plates move horizontally and rub against each other.
The fault takes a rightward bend in Santa Rosa, a feature that may create a greater potential for stress along the fault, she said.
The northern San Andreas Fault that runs through the South Bay, Point Reyes and other Bay Area spots is less likely to cause the next major temblor, researchers suspect. That’s because the devastating 1906 earthquake - magnitude 7.9 - released significant tension along that fissure. The USGS reported a 6.4% chance of a rupture greater than magnitude 6.7 before 2043 on the northern end of the 800-mile fault, compared with a 19% chance of a major temblor on the southern San Andreas near Mojave in Southern California.
USGS scientists found evidence showing the Rodgers Creek Fault ruptured significantly in the early to middle 18th century. They are studying whether the recently discovered connection between the Rodgers Creek and Hayward faults under the San Pablo Bay might indicate they could rupture together, generating a large-scale disaster.