Here's another link to S-O's 'evidence.'
Caveats to pay attention to:
* 'once a strong correlation has been assessed' ( it hasn't )
* 'next step is to verify if a physical mechanism exists which could explain such a result' ( a mechanism has not been verified )
* ' our observed correlation implies' ( is not proven )
* ' it sometimes exists ' ( it must be proven to coincide with large earthquakes )
* 'Earth's underground voltage increases when it exists' ( bookeeping )
* ' increased voltage passing through a fault ' ( requires coincidental evidence )
* ' increased potential initiates additional piezoelectric strain/stress along fault boundary' ( must prove that random, heterogeneous assemblage of quartz grains do not simply cancel out each other's strain, in the absence of a focused, unidirectional force vector )
* ' piezoelectric 'swelling' triggers rupture' ( might it not increase the clamping strength of the asperity and actually 'strengthen' the fault's lock? )
* ' events would be accompanied by atmospheric luminescence' ( already explained by other unrelated mechanisms )
* ' we suggest ( nothing more ) that our statistics-related hypothesis ( corroborated by other statisticians ? ) can qualitatively explain observations ( can they 'quantitatively' explain observations? )
Here's the link
https://www.nature.com/articles/s41598-020-67860-3