If you use 'Newton's cradle' to simulate the effect, you will find that the energy produced will continue to resound in opposition to its impact.
But, if you fire an arrow into a melon - It has to travel about 90% into the fruit to directly displace its opposite skin (intended exit-point).
As far as the earth (as a unit) was concerned - A grain of sand hit it.
Now, when Theia hit it and the moon formed - That was an impact!
To the (eggshell) crust though - I do believe the wave-exit point would have been equally dispersed and most potent only at the weakest points - I don't perceive a giant wall of energy (material) circulating the globe and slamming into itself.
It's all just pebbles making waves, to me.