Hi Chris. If memory serves me "normal modes" are the "free Earth oscillations" that Dr. Lowell Whiteside and Yehuda Ben-Zion wrote a paper about a couple of years ago. It had something to do with the triggering of other quakes. I think this is how the theory about "far field aftershocks" was born.

The Rayleigh surface waves caused by the Sumatra quake traveled around the planet several times before dissipating. Seismic energy was released at such long wavelengths that they were a substantial fraction of the Earth's circumference. Their interference patterns formed standing waves, somewhat like rhythmic oscillations. In effect, the Sumatra quake made the Earth ring with these free oscillations like a hammer rings a bell. Those Rayleigh waves were recorded by the miniPBOs in the San Francisco Bay Area. I remembered thinking at the time as to how this may have affected the faults in the Bay Area. Then I got to thinking how this may have affected the faults through out the Earth.

The "notes" of the bell, or normal vibrational modes, are at extremely low frequencies: the two strongest modes have periods of about 35.5 and 54 minutes. These oscillations died out within a few weeks. Another mode, the so-called breathing mode, consists of the whole Earth rising and falling at once with a period of 20.5 minutes. I don't remember how long this affect was suppose to last, but it was more then a couple of months.

I can't prove it, but I do believe those oscillations caused the quakes in the area of Ecuador. They were at the antipodal of the Sumatra quake and it was in an area that has a lot of seismic activity. A lot of people have dismissed the FFA theory and I'm not really sure why. It is sort of like "ear tones" which are also dismissed either because they weren't taught that, or they don't understand it. If it doesn't fit into their little box it's dismissed. I think this is somewhat foolish, as it may be the step that is needed to get to the top of earthquake prediction ladder. As an analyst for the Air Force I learned early on not to dismiss anything as it may kill you in the end. That doesn't mean you are to stop doing what you are already doing, but it would be wise to file it away for future use. You never know when you might find the other piece to the puzzle. Take Care…Don in creepy town