| Abstract: | We have developed a method to retrieve overcritical PdP reflections from the top of D″ from the data. The differential travel-time, amplitude ratio and phase advance of the reflected PdP waveform relative to the direct P waveform are accurately obtained. Kirchhoff synthetics have been used to model the reflected waveforms for a set of different incidence angles i and velocity contrasts δα at the reflector which were then used as reference wavelets for the deconvolution.The results from a Gräfenberg data set differ markedly from the values predicted by the one-dimensional PWDK model derived from the same data. However, there are large uncertainties in i and δα. This could be caused by the presence of significant lateral heterogeneity in D″ or the need to model other phases which may exist such as the diving waves PDP and PDDP. The method is also applied to two other data examples. The trade-offs between different model parameters are examined. |
