Traveltimes of P and mode-converted S-waves and their reverberations place a tight constraint on the Vp/Vs ratio and their amplitude ratio provides tight bounds on the P and S wave velocity jumps across the main discontinuities in the subsurface structure below a seismic receiver. Seismic P-to-S converted waves have been used for decades to estimate the shear-wave velocity of the subsurface and depths of major discontinuities below a seismic receiver through a method known as the P wave receiver functions. Here, a new and alternative approach is presented using P and all mode-converted shear waves in a probabilistic joint inversion framework to simultaneously estimate seismic properties of the crust (Vp, Vs, and Vp/Vs). These waves are extracted by the autocorrelation of the teleseismic P-wave coda recorded on the radial and vertical component of a threecomponent (3C) seismic receiver. In the application of the methodology, we image the crust along a north-south oriented passive seismic line (BILBY) in central Australia, which traverses multiple geological domains. The overall trend of our inferred Moho follows the long wavelength pattern of the Moho interpreted from the deep seismic reflection line-GOMA parallel to the BILBY experiment. It is also consistent with the reflectivity changes seen at the base of the crust in the GOMA seismic section. Our approach is a cost-effective method and can be used in conjunction with the deep active seismic reflection profiling to obtain additional information, especially at depths where the deep seismic reflection method cannot image.

Open-Access Online Publication: March 03, 2023