Hi Lowell,

I've been watching that area for a while myself. Here is what I think: The Hayward Fault, I'm not sure. I've noticed everyone on this board watches that fault like a hawk for obvious reasons. I think Don has the best theory about the slip on the Northern half and the concern of where that slip is going.

The Calaveras, that is a different story. I feel like that fault is totally ignored, specifically the northern half from about Sunol to the Danville/Alamo/Walnut Creek area. I've been hearing for the past 20 years that this segment has been locked. There was this past week several micro quakes on near it in the San Ramon area. In 90, there were a swarm of 4s and 3s in the area between where the fault ends and the Concord Fault begins. I've heard that at the time USGS was concerned that this swarm may have been foreshocks to a 6+ quake in that region. Obviously this never happened.

So, my thoughts are we will see a 6+ quake in this region in the future, maybe in the next 3-6 years from now? I also think that there is a small possibilty that if there was a strong quake on this segment of the Calaveras, it may provoke a large shock on the Hayward fault within days. I know our history doesn't go back far, but, it would be interesting to know if these 2 faults in this area have had a relationship of that type in the past, one goes, and then the other. They are only about 10 miles from each other, both moving at rapid slip rates, both have not had a large jolt in over 150+ years, and, there is no other major active fault between the two.

As with all things in this state, time will tell. But I think the Bay Area needs to be more aware that there are other dangerous faults besides the Hayward and San Andreas.