Lightning underground can be detect by the EMP generated by the flash of electricity. Two EMP detectors, one above surface and one below surface (~5 km) can differentiate lightnings in the atmosphere from lightnings underground by the arrival time differential at the two stations. Four such pairs of detector can locate the source of the underground electrical flash, including depth information (Multilateration).
The event of lightning underground together with locations of known earthquake zones may predict the likelihood of tremors. Earthquake zones may coincide with regions of crystalline formation underground.
Now who would invest in so many "maybe"s?
