The structure of the sedimentary cover and crystalline crust in the Sichuan Basin and its tectonic implications

SUMMARY The Sichuan Basin, located to the east of the Tibetan Plateau, experienced successive marine and continental depositions since the Sinian. Structures of the sedimentary cover and crystalline crust, for example, thickness and Vp/Vs ratio, are of great significance to study the basin's properties and evolution, which have not been investigated simultaneously. In this paper, we extended the traditional single-layer H–k stacking method of receiver functions to a multilayer H–k stacking approach and applied it to invert for thickness and Vp/Vs ratio of the sedimentary cover and crystalline crust beneath 14 seismic stations in the Sichuan Basin. The observed thickness and Vp/Vs ratio of the sedimentary cover range from 4.2 to 7.5 km and from 1.86 to 2.55, respectively, suggesting unconsolidated sediments containing water or other fluids. Two-layer sedimentary cover was observed beneath eight stations, probably corresponding to the sediment in the Phanerozoic and Precambrian. The observed thickness and Vp/Vs ratio of the crystalline crust range from 33.4 to 41.8 km and from 1.61 to 1.78, respectively, suggesting typical cratonic crust in the Sichuan Basin. Theoretical analyses of H–k stacking were further performed for different types of sedimentary basins, and the results suggest that the multilayer H–k stacking is more effective to study basin's structure with a thick sedimentary layer and thin subsediment crust.