Hi Canie and All,

Though probabilities on major faultlines are a certain sign that they may be likely to give us a good jolt, all to often they show up where no one expects them. Yountville is a perfect example. They still don't know for certain which faultline to attach it to, but it surely wasn't in the list of probabilities before it happened.

With understanding this can and does happen frequently, therein lies the problem. The public has to have an understanding that though the major faults have had good studies done, there are an equal number that are sleepers and the need to prepare doesn't exclude folks in the area's of lesser known faults.

In the Northbay we've had a few that were unexpected by the scientists which include Bolinas, the Rodgers Creek Fault and Yountville. Taking these along with the other quakes in this area that seem to be popping up in unexpected locations Don and I have come to the conclusion that the Rodgers Creek Fault is under stress, but is today possibly locked, so what happens is that you get quakes on either side of it. Of course that doesn't relieve the stress on the RCF and for all we know could increase it by additional stress forces.

The greatest problem that exists with measuring the potential for the RCF having a 7.00 is that there have not been enough earthquakes over time to study. Since the twins in Oct 1969 its been relatively quiet until the last two years. That sends a message also, but in figuring out a timeline for the expected quake(s) it only makes it more difficult. Would a quake occur where they happened before? In Rohnert Park where activity has been increasing or down at the bottom of the fault where the seismic gap is in evidence?

This brings to many questions with few answers.

Petra