This has been ongoing for the past 9 months. But indeed this stretch hasn't been the most active. In my opinion what we are seeing is the early stages of a setup for a large quake on either the Hayward fault or the Calaveras Fault north of this location. What the time frame of that would be, who knows, months, years, etc. I'm guessing years, but when that quake hits scientists will be able to look back and see these were all foreshocks. If I had to guess I would say these are foreshocks to an eventual quake on the Hayward fault. The Calaveras Fault became active in the years prior to Loma Prieta and the 1906 quake as well. Also remember this is the same area a 5.6 quake hit in 2007. Its been about 3 years but I felt like that was the kick off quake to all this activity now.