Old folk tales told of "sprites" or weird flashes of light just before an earthquake. They were just thought to be myths until one was spotted by a satellite over an earthquake just before the quake happened. As it seems to be turning out sprites are very high voltage but very low amperage discharges of electricity from the piezoelectric effect of certain piezoelectric rock formations under increases in pressure. While lightening is also high voltage it is also high amperage so it is easier to spot than a sprite since it releases orders of magnitude more energy than a sprite. You create a mini sprite every time you push the striker button on your propane grill lighter. It is the same thing on a miniscule scale. To get some idea of the voltages involved in a piezoelectric sprite just consider the following facts...

1 - It takes 30,000 volts to jump a spark one inch in dry air.

2 - The piezoelectric igniters I have seen on grills typically have about a 1/16" (.062") spark gap. That means that they need at a bare minimum of 1875 volts, but will need a much higher voltage to insure reliable spark. All that from a piezoelectric crystal less than an inch long.

3 - While your gas grill lighter uses a crystal of approximately 1/4" in diameter and less than an inch long, the piezoelectric rock formations that produce the electric fields can be many miles long wide and deep. So even with less force per inch than it takes for a gas grill igniter to work the piezoelectric formation can produce some truly amazing voltages. And this is what piezoelectric earthquake detection is looking for.

WOW, I will be waiting to see what caused this one. Obviously it isn't a salt dome failure in a swamp. Four football fields long, my goodness that is 1200 feet long by 30 feet deep. Does it say anywhere just how wide it is.

I'm thinking that if that one grows much more it might be cheaper to re route the road than to fill the hole and restore the old roadway.