Hello Russell..I have not read on this in 15 or 20 years, but I think the answers are, yes, yes, yes, and "depends on what you mean by oscillations". Also depends on what you mean by failing, but I recall that there is some sort of sound or other "emmission" before it breaks. If you are headed in the direction of eartones, the problem is that in these tests whatever it is that occurs is measured, but in the case of earthquakes/eartone/whatever, it is not generally measured...John probably should add to this...but the failure before earthquakes may be too small a patch and too deep to be measured near the surface...although some percentage (is it 10%?) have foreshocks...
Chris