Hi John. “Soft fault” Would that be the same as “soft-link faults?” The description you gave Petra sounds a little like it.

I don’t think the Rodgers Creek fault falls into that category. I will admit though that the history of this fault isn’t well known. It is believed the last major quake was around 1600. This would be the segment of the fault between Santa Rosa, maybe a little further south and San Pablo Bay. This was determined by trenching at 3 locations. However we both know that if you don’t dig the trench in the right location you’re not going to find anything. For all purpose and intent there is virtually no creep in this segment of the fault.

The Pinole fault in the bottom of San Pablo Bay may be a soft-link fault in that it could be a connection between the Hayward fault and the Rodgers Creek fault. This fault is also a fault where the history of quakes isn’t well known. There are some indications that it is a thrust fault. If memory serves the “first motion mechanism” was “pure thrust.” It is a northeast/southwest trending fault. Take Care…Don in creepy town