Roger/EQF
In principle, I believe ,there could be something like EM signals.Logic is like this
The portion of Quartz inside the crust may develop Piezoelectric effect when applied mechanical pressure or stress.when crust is under pressure (due to either tectonic movement as you say it or due to tidal pressure ,as I see it).These piezoelectric effect is nothing but EM signals as EQF says.This is just a scientific logic,rest of the things remains to be proveed
Amit