Some seismological tools. Three-dimensional mantle structure. Radius and topography of the outer core

We recalled the laws of refraction and grape theory in seismology, in particular the coefficients of reflection, refraction and conversion at structural discontinuities. We then described the work that has led to a precise estimate of the core radius (volume waves and eigenvibrations), the ellipticity of the CMB(core mantle boundary ) and its topography, which is still very poorly known, except at very long wavelengths (degree 2).