Have you been in an earthquake before? I remember sleeping during a quake and then waking up right before the main shock hit. I’m not sure what woke me up, it could’ve been a preliminary shock, but I very vividly remember being jolted awake right before the earthquake wave hit. It’s entirely possible that an electromagnetic wave precedes a shock, but it’s unlikely that there are significant waves hours beforehand if there’s actually a causal relationship to the movement of the plates themselves.

It would be far more likely that the EM pulse happens with slightly faster propagation than the kinetic pulse (like milliseconds, not hours).