Structure of the Crust and Uppermost Mantle Obtained from High-Resolution Receiver Function Analyses

English Abstract:

Receiver Function (RF) analyses are important in detecting seismic structure of the Earth’s crust and mantle. RF calculation is an unstable deconvolution procedure. Appropriate regularization is generally required to obtain sufficiently stable and accurate solutions. Through deconvolution, influences of structure near the seismic source and the source time function are removed, and comparable source-equalized RFs may be stacked to enhance signal-to-noise ratio. A high-resolution stable spline-based RF calculation approach is developed. Through synthetic RF modeling, it is demonstrated that the spline method is noise-resistant and substantially more accurate than conventional water-level spectral division and iterative deconvolution methods.

We test the spline method’s efficiency for real-world applications with broadband seismograph data recorded at stations near the eastern Tibetan Plateau and northern Rocky Mountains. Moho converted phases are clearly seen for all the stations. Normalized and stacked spline-based RFs have higher resolution than those calculated with the conventional methods. The maximum peaks on the spline-based H-k stacking images are substantially more conspicuous. The RFs better calculated with the spline method lead to improved determination of optimal crustal thicknesses and Vp/Vs ratios with greater resolution and clarity. The new RF results are compatible with existing geophysical and geological information available for some of the stations. Crustal thickness, Vp/Vs ratio, Moho sharpness and structural complexity vary significantly for the stations studied which sample a variety of distinct geological provinces.