waves produced by earthwuakes travel through the earth at speeds depending on the medium density, and they also refract when meeting a change in medium. these waves, when detected in various parts of the world, build a picture of the structure of the earth, with its differentiated layers: crust, asthenosphere (low-velocity layer), the mantle, the liquid outer core and the solid inner core (known to be solid through detection of shear waves)
so, presumably, this is all a conspiracy too?
is the global network of seismometers, several of which i have operated myself, all a lie?