Hi Steve. The West Napa Fault is listed as having a creep rate of 1.0mm per year. It starts at 38.16N/122.24W and end at 38.41N/122.37W for a length of 30Km with a width of 10Km. It is thought to be able to have quake up to M>6.5.

You are more then likely aware of the M>5.2 Yountville quake a couple of years ago. At first it was thought to have occurred on the West Napa Fault, but now it is thought to have occurred on an unknown fault.

It seem though that Sebastopol geologist Eugene Boudreau gets rattled every time he hears or reads that Sunday morning's Napa Valley earthquake occurred on an "unmapped" or "undiscovered" fault.

"I told the USGS in 1976 about this fault," Boudreau said Tuesday over documents that substantiate that he announced 24 years ago there is a fault running west of Highway 29 and the mapped West Napa Fault. See the link for his story. Take Care…Don in creepy town

• West Napa Fault