I sent an inquiry about the Geysers being included and Mammoth being excluded. Both are volcanic areas, however, the development of injection of sewer fluids into the Geysers has had a definite effect upon its seismic behavior. I doubt The Geysers will ever deliver a 6.0, though a lot of little 3's and the occasional 4. However, Mammoth is always active to one degree or another, has had 6.0 quakes and is not influenced by man made events.

I think if one were looking for true clustering events they would have to check the injection schedule at The Geysers to see what was up or down that week/or day.

We'll see.

Petra