From all the posts on here the consensus seems to be that splash damage occurs whenever a wall section is destroyed and it affects any equal or lesser value wall section within 5 tiles of the 4 cardinal directions of the destroyed wall.
Now, on my claim I already had some kind of wall beyond my core area in some areas which is 2 tiles away so I wanted to destroy them and I thought this would be neat way to see splash damage in action. I destroyed several sections and was surprised to find that only one of the destroyed walls caused splash damage to my core wall, as shown below:

The pic shows me after I have already destroyed several sections of that wall I am facing, which used to continue down parallel to the wall on the right beyond the pictures boundary to the south. But if you notice on my core wall to the right, only 1 section has any damage to it from destroying all the wall sections to the wall on the left.
After taking this pic I continued destroying that wall and still dont see anymore splash to my wall on the right.
Why?