Roger...when I suggest quakes in California are clustered I am taking into account aftershocks...meaning that I'm just looking at the map and see a week where there are no M3s or few, and few smaller quakes, and then weeks where there are 3s or 3s and 4s scattered about. The small aftershocks of 3s and 4s don't visually do much to such patterns..when looking at the state quake map. I guess you would have to remove aftershocks in a radius depending on magnitude...for a M2-3, 1 km, for a M3-4, 2 km, etc (or whatever numbers make sense). I guess that this would not remove swarms of small quakes, unless you use a larger area. I suppose you could remove any quake, smaller or bigger, for 10 days after a M2-3 over 10 km radius, for 3-4 over 20 km radius, , for 30 days for M 4-5 over 30 km, etc...(for 1 year for a M6 over 50 km?).
Chris