I could try to jump into this, but I don't know much about it. I'll just note there have been been attempts to see EM signals with instruments (again, much more accurate and straightforward to interpret than people's ear tones).

Only one case, Loma Prieta by Tony Frasier-Smith, gave an interesting result, and since not even the smallest detectable earthquake accompanied his observation, there certainly was not much cracking rock or fluid percolation involved. Tony has now failed to see any signal for several other earthquakes at greater distances (still less than people like King claim to see in most cases even for far smaller earthquakes).

It is not clear there is any EM signal present to interpret.