Seismic autocorrelation: structure along the Bilby array and link to Marla line in central Australia

Autocorrelation of the immediate coda of P waves provides an alternative to traditional receiver functions. Working at higher frequencies enhanced information can be extracted on the Moho surface. We show that the autocorrelation process is equivalent to a virtual point source at the surface, and this enables the extraction of local reflectivity. ACC (Auto-Correlogram Calculation in Seismology) software is used to process and analyze teleseismic P-wave coda recorded along the Bilby array aligned north to south and the Marla array aligned east to west in central Australia. Clear signals can be extracted for the Moho, mid lithospheric discontinuity (MLD), and the transition from the lithosphere to the asthenosphere (LAT), exploiting reflectivity estimates in different frequency bands (up to 5 Hz upper bound). The Moho of Bilby lies at 40 km or deeper, the MLD around 80-90 km depth, and the LAT between 130 and 180 km depth. A cross-check on the nature of the seismic structure is provided by the intersection with the dense Marla array (MAL) in an east-west direction near stations BL19 and BL20. Consistent reflectivity results are extracted in orthogonal directions.