We began with a historical introduction detailing the main stages since the discovery, thanks to seismology, of the existence in the earth of a liquid core (Oldham, 1906) and the discovery of the seed (Lehmann, 1936). Of particular note is the work of Birch (1952) to establish the contrasting composition of the mantle (silicates) and core (iron alloys) and the confirmation of the solidity of the seed (dziewonski and gilbert, 1971), and the discovery of the presence of seismic anisotropy in the seed through the study of eigenmodes (cf. woodhouse et al., 1986) and core volume wave propagation times (morelli et al., 1986).
We introduced some basic notions of seismology, the existence of two types of seismic waves (compressional and shear), their respective properties, and the nomenclature of seismic "phases". We present seismic tools sensitive to core and seed structure, PKP volume waves and their various branches, waves reflected on the surface of the seed and the core-mantle boundary (CMB), and the spectrum of the earth's natural vibrations. A spherically symmetrical ("1D") seismogenic earth model established 30 years ago, PREM(Preliminary Reference Earth Model, Dziewonski and Anderson, 1981), still serves today as a very good reference model.
Finally, we have mentioned the importance of work in materials physics at high pressure and temperature, which, by comparison with the elastic parameters provided by seismology, enables us to identify the mineralogical composition of the deepest parts of the Earth.
