Thanks for the reality check, Chris. I do have a tendency to overstate my case. However, though magma and water do certainly exist subsurface, I did not (and do not) consider those germane to the discussion, except in those cases where Steve might specifically refer to detecting local "magnetic phenomena." But his explanation refers repeatedly to "regional" effects. And "triangulat[ion of signals] from sites perhaps thousands of miles away." Magma exists mostly in only very localized locations, and subsurface water, though ubiquitous, seems, both by virtue of that very ubiquitousness, and its existence in extremely stable formations which do not change day-to-day or week-to-week, as well as its having no known propensity for generating electromagnetic signals, to be a poor candidate for what Steve is talking about.

BUT - you did bring me up short with your mention of the fluids in subduction zones. Those fluids, primarily seawater stored in subducted sediments and the rising magmas that result, are regional in extent, and I suppose could fill the bill for Steve if he limited his discussion to subduction zones.

Though I can't prove it, I'm pretty sure Steve shares the meme common to many seismological dilettantes (my earlier self included in that category) of a vast network of subterranean interconnected conduits and reservoirs of magmas and other infernal fluids surging constantly beneath our feet and causing all kinds of mischief.

I'm sure I'll be (rightfully) criticized for venturing beyond what Steve has actually said, but I gotta be me!

Mike Williams