4 northern California faults primed for big quakes

A new study says four stretches of fault running under northern California are primed for quakes of magnitude 6.8 or more.

The study by scientists with the U.S. Geological Survey and San Francisco State University looked at 35 years of measurements along northern California’s San Andreas fault system. Geologists looked for fault creep, meaning tiny surface movements along fault lines that help ease tension.

The study, released Monday, found that close to one-third of the 1,250 miles of fault lines in the San Andreas fault system appear locked. That means there is no fault creep on those stretches, and pressure is building for an earthquake.

Geologist James Lienkaemper of the U.S. Geological Survey says the study found the Green Valley fault in Napa and Solano counties appears ready for a major quake. That fault is near the dams and aqueducts that supply much of California’s water.