Eartones are harder to evaluate than things that are measured-that are recorded, like the magnetic field. I'm not going to look into the literature mentioned above, but maybe someone else can link to it or post it here. After we see what has already been done, then someone (Roger) could make plots like he is doing for FFAs. But, I really should spend time with Lowell's thesis first..... I personally don't think there is any relation between eartones and earthquakes (beyond that I guess earthquakes can make a lot of noise....). Chris