Mike...not really correct to compare changes in stress to the total weight of a column of rock. I think a bar is equal to 1 atmosphere, which is equal to 10 meters of water. (I don't like to use megapascals). For rocks of density 2.65 (granite), it would take about 4 m of rock for a load of 1 bar. So, if quake was at 12 km (for example), would be 3000 bar load. Most large quakes release less than 100 bars of stress. Static stress changes of a bar or less can trigger quakes (Landers and the ~M6.5 in San Bernadinos comes to mind). So, a couple meters of rock load or unload could trigger a quake if it was all primed and ready to go.

As for distinguishing whether the trigger was fluid pressure vs weight...well, it might be interesting to just see if there is any relation with rainfall, and worry about how that might work later. I don't know if we would be dealing with statistics of small numbers trying to find a weak effect. Won't know if we don't look. But, I'm not going to look....that is why I am trying to pawn this off on someone else...you for example.

Chris