I don't know the answer either, but it wouldn't be nonsensical in my opinion to have the spell not impact things that are hidden underground when the spell is dropped, allowing them to then pop up and not be invisible. However, the offensive troops that are also invisible shouldn't trigger the traps.
Walls aren't invisible. Same for siege machines.
RIP using 10 zap 2 quake on scatters for a couple different armies I've had fun with lately. However, there is more to come, so perhaps we are getting more offense not yet announced.