There are some really simple physics involved here. For example, from first principles (i.e no assumptions) we can calculate the average density of the planet. We can also collect samples of the upper part of the earth and realize that there is a density deficit based on the average density of the upper part of the earth. The conclusion is quite simple that there must be denser material below the crust and upper mantle. We also know (from first principles) how certain waves behave. Shear waves cannot penetrate liquids (for example). We know (based on diamond anvil experiments) the material properties of matter at certain P-T conditions. In short, if you want to claim some kind of special earth structure, the onus is on you to provide experimental evidence in support of that structure. Mere conjecture is no good. I've mentioned this elsewhere, Walt competely eschews the scientific literature. He will not submit his ideas (despite an invitation to do so) to science. He does not present his idea at major scientific meetings. All he does is peddle his nonsense (IMO) to those pre-disposed to think that their salvation hinges on the validity of the Noachian flood. There is no real polite way to say this, but Walt needs to put up or shut up. If he has good scientific ideas and if his hypotheses have merit, then he should not hesitate to bring them to the forefront. If he is right, he will never get the credit he deserves because he has never put his ideas on the line. In fact, you've been more bold with proclaiming his ideas than Walt ever has. I give you credit for bringing them up on this forum. Have you ever wondered why Walt won't bring them up himself on a forum like this? Have you ever wondered why he does not submit his ideas for publication? Have you ever wondered why we've never seen him present his ideas at an AGU or GSA meeting?
Cheers
Joe Meert