Simultaneous Characterization of Crustal and Sedimentary Layers Using Receiver Functions

Abstract:

Converted P-to-S phases from velocity discontinuities are widely used to investigate layered crustal and mantle structure beneath a seismic station. However, strong reverberations in unconsolidated or poorly consolidated sediments frequently mask the converted phases from deeper crustal and upper-mantle boundaries. Such reverberations are believed to be caused by the converted P-to-S phase between the sedimentary and basement layers. Here we proposed and tested an approach to effectively remove reverberations associated with the sedimentary layer. Synthetic receiver functions (RFs) are produced for a model with a thin sedimentary layer overlying a consolidated basement. Auto-correlation is firstly conducted on each of the synthetic RFs to determine the strength and period of the reverberation. A frequency domain resonance-removal filter is then applied to remove the reverberations. The P-to-S converted phases and their multiples from the Moho are clearly observed on the resulting RFs. The RFs are then time-corrected to remove the effects of the sedimentary layer, and the thickness and Vp/Vs of the consolidated crust are determined using the corrected RFs. Finally, the resulting crustal thickness and Vp/Vs are used as input parameters in a grid-search procedure for the thickness and Vp/Vs of the sedimentary layer. Testing using synthetic data demonstrates that this technique is efficient in resolving seismic structure beneath stations sitting on a layer of loose sediment. The efficiency and validity of this method are further examined by processing teleseismic data recorded at station NE68, which is located in the Songliao Basin in northeast China. The resulting sedimentary and crustal structures are consistent with those obtained by Tao et al. (2014) based on the wavefield downward continuation and decomposition method.