Seismogram and differential seismograms computed with respect to shear‐wave velocity for the layers indicated in Fig. 1. The uppermost trace is the velocity seismogram (m s^{− 1}), which is determined using an instantaneous point‐source double‐couple (δ=37°, λ=283° and h=33 km) located at a distance of 400 km and at a strike–receiver angle of 260°, The seismograms are scaled with a moment of M₀=6.5 × 10¹⁹ N m. The remaining traces are the differential seismograms. The number at the top right of each seismogram indicates the layer number (Fig. 1b) to which the differentiation refers. A Gaussian roll‐off filter with a corner frequency of 0.85 Hz is applied to all traces to remove ringing due to truncation of the spectrum. (a) Radial component; (b) vertical component.