Seismic waves are used to investigate the interior of the Earth
And being in torments in Hades, he lifted up his eyes and saw Abraham afar off, and Lazarus in his bosom.
“Then he cried and said, ‘Father Abraham, have mercy on me, and send Lazarus that he may dip the tip of his finger in water and cool my tongue; for I am tormented in this flame.’
(Luke 16:23-24) NKJV

Here is the diagram that we saw for the first time on September 7th. The popular science interpretation of data from seismic waves.
The question we should ask is : why are the lines depicting wave propagation curved?
The answer: It’s theoretical.
If we want to be empirical: Let’s use straight lines.
But Abraham said, ‘Son, remember that in your lifetime you received your good things, and likewise Lazarus evil things; but now he is comforted and you are tormented. And besides all this, between us and you there is a great gulf fixed, so that those who want to pass from here to you cannot, nor can those from there pass to us.’
(Luke 16:25-26) NKJV
Volume of Earth’s Mantle
Factor | Symbol | Radius | Volume |
Earth total volume | p | 6,371 km | 1.08E+12 m3 |
Volume of core and great gulf | g | 4,100 km | 2.89E+11 m3 |
Volume of mantle material | p-g (m) | 7.95E+11 m3 |

The total volume of present day Earth is 1.08E+12 m3
The volume of material in the crust and mantle is found by subtracting the volume of a sphere of radius 4,100 km from the volume of a sphere of radius 6,371 km