Complex Crustal Deformation Beneath the Cathaysia Block in South China: Evidence From Receiver Function Analysis

Abstract

Abstract By harmonically fitting the arrival times of the P‐to‐S converted phases from the Moho, we systematically investigate the crustal anisotropy beneath the Cathaysia Block (CaB) and the surrounding areas in South China for the first time. The measured anisotropy parameters show strong lateral variations with an average splitting time of 0.35 ± 0.12 s. The resulting fast directions exhibit clear geographic variations with two possible boundaries that separate the CaB into three parts. The inconsistent fast direction of crustal anisotropy among each part, and the comparisons with teleseismic XKS splitting measurements indicate that the mechanisms of crustal deformation vary between distinct regions. The crust deforms coherently with the upper mantle in the western CaB, which is possibly driven by mantle flow. The fast directions of crustal anisotropy in the central CaB exhibit a radial pattern and show large discrepancies with XKS splitting measurements. We suggest that the crust has a complex deformation mechanism in this region. We propose a new scenario that emphasizes the interaction of the crust and upper mantle for interpreting the radial‐patterned crustal anisotropy, which involves the processes of subduction plate rollback, asthenospheric upwelling, crustal melting and lithospheric mantle intrusion. The fast directions of crustal anisotropy in the eastern CaB are dominantly parallel to the continental margin, suggesting subduction‐controlled crustal deformation in this region.

Keywords

• Cathaysia Block
• receiver functions
• crustal anisotropy
• complex crustal deformation