Constraining Crustal Properties With Bayesian Joint Inversion of Vertical and Radial Teleseismic P-Wave Coda Autocorrelations

The sensitivity of seismic compressional and shear waves and their velocity ratios to rock lithology, pore fluids, and high-temperature materials makes these parameters very useful for constraining the physical state of the crust. In this study, we develop a joint inversion approach utilizing both radial and vertical components' autocorrelations of teleseismic P-wave coda for imaging the crust by simultaneously characterizing the crustal Vp, Vs, and Vp/Vs ratio. Autocorrelations of the radial and vertical components contain P and S waves that are reflected from the subsurface. Therefore, joint inversion of them can account for the variations of both Vp and Vs, and consequently, the Vp/Vs ratio. Synthetic inversions show significant improvement in the estimation of these parameters compared to those from the inversion of either, P receiver functions or the autocorrelation of the vertical component. The velocity models inferred from the application of the approach to teleseismic data recorded along a north-south passive seismic profile (BILBY experiment) in central Australia reveal a distinct pattern of the Moho and the Vp/Vs variations across the crustal blocks/domains. The general trend of the Moho structure corresponds well with the change of the reflectivity that can normally be seen at the base of the crust and also with the Moho estimated from previous studies including the deep seismic reflection profiling method. The Vp/Vs structure at depths greater than 10 km shows dominant high values beneath locations where the crustal domains interact (e.g., at transition from one domain to another).

Automated summary

The study developed a joint inversion approach using teleseismic P-wave coda autocorrelations to simultaneously constrain the crustal Vp, Vs, and Vp/Vs ratio, showing significant improvement in parameter estimation compared to traditional methods. The velocity models inferred from the approach along a seismic profile in central Australia revealed distinct patterns of Moho and Vp/Vs variations, corresponding well with previous studies and reflecting interactions between crustal domains.