E-W and S-N Differences in the Sedimentary Cover and Crystalline Crust in the Cratonic Ordos Basin From Receiver Function Analysis

Thicknesses and Vp/Vs ratios of sedimentary cover and crystalline crust are key parameters to study basin properties and evolution. In this paper, we develop a hi-ki method of receiver functions to estimate the thickness (h) and Vp/Vs ratio (k) for each layer based on the arrival times of Ps converted and PpPs multiple phases of the layer, and apply the method to invert for h and k values of the sedimentary and bedrock layers in the Ordos Basin. S-N and E-W differences in structure across approximately 109?degrees E are observed in both the sedimentary cover and crystalline crust. The sedimentary thickness generally increases from east to west and reaches 7.9 km on the southwestern edge. Vp/Vs ratios are complex with an average > 1.9 and overall are lower than 1.75 in the northwestern part. The bedrock thickness and Vp/Vs ratio vary from 31.2 to 45.0 km and from 1.60 to 1.82, with average values of 39.62 km and 1.74, respectively. The crystalline crust still retains the long-term cratonic stability and characteristics. The observed S-N and E-W differences in the sedimentary and bedrock layers may be the combined results of inhomogeneity in original nucleation and later complex and long-term tectonic evolution. Plain Language Summary A hi-ki method of receiver functions is developed and used to estimate the thickness (h) and Vp/Vs ratio (k) values for the sedimentary and bedrock layers beneath seismic stations in the Ordos Basin. S-N and E-W differences in structure across approximately 109 degrees E are observed in both the sedimentary cover and crystalline crust. Vp/Vs ratios typical of intermediate-acid rocks and thicknesses of similar to 40 km are observed in the crystalline crust of the Ordos Basin, suggesting that the Basin has retained its cratonic nature and stability. The observed differences in the sedimentary cover are likely to result from a combination of the inhomogeneity in original nucleation and later complex and long-term tectonism of the Ordos Basin, such as westward tilting from the Triassic to late Miocene and multiple uplifts with denudation, especially from the Late Cretaceous to Paleocene. Differences in the crystalline crust may be related to the collisions between the Yinshan Orogen belt and the Ordos Basin, and between the Ordos Basin and eastern block in the Paleoproterozoic, and the uplift and eastward expansion of Tibet in the Cenozoic.