Jane..yes. I've been posting here for I think 4 years, and early on it seemed as if it was an accepted fact to some posters that solar activity could trigger earthquakes. There is probably some of that in Lowell Whiteside's thesis. I recall back from when Lowell posted here that he would increase the magnitude of a prediction by 0.5 if there was a large solar flare. I was open to this, and at the time probably though there was some effect, when I first started posting here. I sat between 2 well-known seismologists at a SCEC meeting about a decade ago and they both knew Lowell and one had a mechanism why the fluctuating magnetic fields during a geomagnetic storm should trigger quakes. But, with suggestions by me, Roger Hunter looked into it for the largest flares the last few decades and M5 and larger global quakes. There did not seem to be any effect. But, sometimes there are large flares and the mass ejection misses the earth and we don't get a large magnetic storm....so Roger had not tested a list of the largest magnetic storms against smaller quakes...might be interesting to look at volcanic areas like Coso and Long Valley and Yellowstone. During the last solar maximum a couple years ago there were some huge solar flares and huge magnetic storms, and just casually observing the California and global seismicity pages, nothing jumped out as unusual to me.
So, it seems more likely that shifting strong magnetic fields would have a better chance of doing something than just a decreasing field...if there is any affect at all.....Chris