Fig. 4: Seismic reflections models.

Reflection coefficients for vertically incident \(P\) (a–d) and \(SH\) (e–h) waves on a bridgmanite to post-perovskite interface. The figure shows the reflection coefficients as a function of the wavelength of the incident wave for six Pv-pPv transformation characteristic times \(\tau\) ranging between \(1{0}^{-1}\) and \(1{0}^{4}\) s for an infinitely sharp boundary (a, e), or a Pv-pPv coexistence layer of 10 km (b, f), 50 km (c, g), or 100 km (d, h). For a sharp boundary, reflection coefficients are 0.5 and 3.5% for \(P\) and \(SH\) waves, respectively. For thicker Pv-pPv coexistence layers, they can be enhanced or reduced by up to two orders of magnitude depending on transformation kinetics. The wavelength dependence of observable reflections (e.g. \(> 3\)%) could be used to constrain the thickness of the Pv-pPv coexistence layer.