Thx for your thoughts. Here are also some thoughts:

You may wish to know that geomag storms create ULF waves (near the polar regions generally)...these may also show up as "long period" and possibly cause seismo interference (read "no actual ground motion"). This effect must be weeded out if it is present....

Still not clear on what "1st up motion" means....

re: time - Yes...I know that a geomag storm is about/at the earth....