Chris in S.,

I forgotten about the co-incidence of names. Chris Russell is the EM expert at UCLA, and he doesn't post here.

I'd skip the visual test and just perform a cross-correlation to see if there is any relation between the plotted time series. It's a one-line command in MatLab, for example. It's not definitive to perform a critical test visually, unless the match is striking, which it is not. If you suspect gradients, cross-correlation with the derivative, or make an analytic signal with a Hilbert transform to look for a phase shift.

But then again, EQ doesn't consider us qualified to have an opinion.

John