That's silly. You're saying there is no way for a wave to propagate through any shape other than a sphere?
No, its more like, if it propagated throught a disc it would be just felt on the other side of the dics, so we'd have two separate earthquakes magically happening at the same time and by pure coincidence if you accept the RE theory for a moment these two spots seem to opposite each other but no, it is purely coincidental as earth is indeed flat.
Graph for those who didnt understand:
-X--
-- | --
- | -
- | -
-- | --
-Y--
(RE theory, btw)
Two spots where earthquake is felt marked by X,Y
FE theory:
I-------X----------------------------------------Y---------------I
--------X'----------------------------------------Y'--------------
Two places where earthquake is felt marked by X,Y. Ice wall marked by I ;]
As you can see, when earthquake X propagates, its felt on the other side of the disc (X'), shame we cant check that.
So if earthquakes are noticed in X and Y simultaneusly it must be coincidence.