I seem to remember a while ago in Zafaria, I was beating a Longdreamer Shaman (http://www.wizard101central.com/wiki/Creature:Longdreamer_Shaman) when the Shaman casted an Earthquake on me. Since I was ice, I had to use a lot of blades - and so when The Shaman casted an earthquake I was really mad. But something I still can't believe happened is that when he took all my blades off, he somehow took DAMAGE from taking off all the blades! Is this some sort of glitch or, an actual implement into the game I have never known about?
Earthquake does not have any kind of a backlash. That is to say, it does not cause any damage to go 'backwards' onto the wizard casting it. The only spells that do cause damage to the caster are Death spells (like Dark Pact, Feint, Empower, Sacrifice, etc), or some Shadow school spells.
Long-dreamer Shamans are Myth school only. They don't cast off-school spells. So I'm not sure what you saw - either you misinterpreted a DoT that you'd already cast upon them as coming from the Earthquake, or it was a some kind of bug.
Logan LegendShade
Alia Misthaven
Emma Ravencaller