Earth currents appear to be the strongest determinant as to the physical location of c2g strikes.
The researchers at DML propose it's because the Earth currents are eating away at pipelines and speeding up corrosion.
DML has learned GIC are more active along fault lines just like Earth currents and lightning.
Earth currents also occur in shallower stratigraphic layers from 5,000-30,000-foot depths.
Lightning forms when "dart leaders" descend below a thunderstorm, which typically are between 10,000-25,000-foot elevations, seeking a connection to Earth currents.
Faults are electromagnetic hot zones where electrical currents from the atmosphere are interacting with the subsurface currents called telluric or Earth currents.