Gday Helios, I am glad you mentioned that development re earthquakes, I saw that news hit a while back and didn't have the time to read up on it, and ultimately with everything going on in life at the moment forgot about it. It does sound a bit out there, but I have no reason to *disbelieve* it is possible, the physics buffs and the top tier geologists will have a better thought process for proving or disproving the theory in time, but with my background in Automotive/Electronics and with my base level understanding I reckon they could be onto something.
Some rambling electrical theory thoughts...
One of the most common piezo crystal materials is high purity quartz - SiO2. If you have a piezo crystal stack and you introduce force upon it for instance weight directly, or air force from a sound wave, it will induce a small voltage across the stack, proportional to the force applied, which is polarised (kind of) in the direction of the application of force...so there's a potential difference (voltage), a difference in abundance of charged particles from one side of the stack to the other, but no current flow as Quartz is an insulator.
If you introduce a voltage across a piezo stack, it changes the orientation of the crystal lattice and ionizes them somewhat, leading to a change of the physical size of the wafers within the stack (talking in very small scale here). Once again no current flows per se, as the quartz is an insulator.
If the stack is in contact with substance that is electrically conductive however, be that a solid, liquid or gas, these voltages have potential to discharge if there is a path for the electrons to move in. If you discharge the voltage, you have current flow, and you have a concentric magnetic field around the conductor of which its intensity is proportional to the voltage and current flow, whilst the current is flowing.
Obviously these points I make are in respect to electronics ie highly finished and refined end product, not a raw, unprocessed quartz body but the fact the principals exist in my mind at least gives a bit of credence to the possibility of earthquakes influencing the gold endowment (or any magnetic or conductive material for that matter) of quartz veining, especially if they are still in contact with mineralized fluids from deep underground.
Food for thought. I'll definitely be on the hunt to read up on it all again this week.
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