Constraining crustal structure in the presence of sediment: A multiple converted wave approach

Abstract

Receiver functions are sensitive to sharp seismic velocity variations with depth and are commonly used to constrain crustal thickness. The H-κ stacking method of Zhu & Kanamori is often used to constrain both the crustal thickness (H) and VP/VS ratio (κ) beneath a seismic station using P-to-s converted waves (Ps). However, traditional H-κ stacks require an assumption of average crustal velocity (usually VP). Additionally, large amplitude reverberations from low velocity shallow layers, such as sedimentary basins, can overprint sought-after crustal signals, rendering traditional H- κ stacking uninterpretable. We overcome these difficulties in two ways. When S-wave reverberations from sediment are present, they are removed by applying a resonance removal filter allowing crustal signals to be clarified and interpreted. We also combine complementary Ps receiver functions, Sp receiver functions, and the post-critical P-wave reflection from the Moho (SPmp) to remove the dependence on an assumed average crustal VP. By correcting for sediment and combining multiple data sets, the crustal thickness, average crustal P-wave velocity and crustal VP/VS ratio is constrained in geological regions where traditional H- κ stacking fails, without making an initial P-wave velocity assumption or suffering from contamination by sedimentary reverberations.