Receiver Function Velocity Analysis Technique and Its Application to Remove Multiples

Abstract

Results of P wave receiver function (RF) analysis (e.g., H‐κ stacking, common conversion point (CCP) stacking, and migration) depend on the velocity models employed. Converted phases of crustal and upper mantle discontinuities are often interfered by multiple reflections from shallower structures, adding further complexity to the interpretation of P wave RF images. In this study, we propose a receiver function velocity analysis technique (RFVAT) that can constrain the velocity structure above discontinuities and remove multiple reflections arising from target discontinuities. By scanning the amplitude spectra of the Ps and PpPs phases, we can obtain precise arrival times of these phases for interfaces above 250 km (errors < 0.13 s) and derive the average velocities and thicknesses of the layers between interfaces in the crust and upper mantle. Synthetic experiments are used to demonstrate that crustal and upper mantle discontinuities can be coherently identified and that multiple reflections can be effectively removed in the CCP stacking images of P wave RFs using the RFVAT even with low signal‐to‐noise ratio data. By applying the proposed RFVAT to real P wave RF data from the northeastern part of the North China Craton, we achieve an improvement in CCP stacking image of lithospheric discontinuities, especially for the lithosphere‐asthenosphere boundary (LAB). Our P wave RF images reveal distinct lateral variations of the LAB depth. The lithospheric thickness extends to ~120 km beneath the central orogenic belt and decreases sharply to ~80 km at the west edge of the eastern block, consistent with previous S wave RF studies.

A Taxonomy of Upper‐Mantle Stratification in the US

“…This is the opposite behavior for the Ps-converted waves that do not experience top-side reflections. These conversions arrive later for earthquakes located closer to the station (Ryberg & Weber, 2000;J. Shi et al, 2020).…”

“…This is the opposite behavior for the Ps‐converted waves that do not experience top‐side reflections. These conversions arrive later for earthquakes located closer to the station (Ryberg & Weber, 2000; J. Shi et al., 2020). Depending on the station location, data quality, and depth to other discontinuities beneath a station, crustal multiples may not always be easily identified in the receiver function stacks.…”

A Taxonomy of Upper-Mantle Stratification in the US

“…These conversions arrive later for earthquakes located closer to the station (J. Shi et al, 2020;Ryberg & Weber, 2000). Depending on the station location, data quality, and depth to other discontinuities beneath a station, crustal multiples may not always be easily identified in the receiver function stacks.…”

On the Detection of Upper Mantle Discontinuities with Radon-Transformed Ps Receiver Functions (CRISP-RF)

“…The Radon model reconstructs each wavefield contribution at the required slowness p with the correct time-shift q i p 2 , which is parabolic in slowness with the curvature q as the coefficient. To better understand this approximation and why it can separate direct conversions from multiples, consider the Taylor expansion of the arrival time for each wavefield contribution given a single-layer model with thickness h, compressional velocity α, and shear velocity β (Ryberg & Weber, 2000;Shi et al, 2020):…”

“…Recent extensions of the slowness slant stack methodology for global body-wave imaging improve resolution by incorporating the notion of the time-and-space locality as well as phase-coherence before stacking (Ventosa et al, 2012;Ventosa & Romanowicz, 2015a, 2015bZheng et al, 2015). Similar ideas have been applied to Ps-RFs in many variations (Guan & Niu, 2017;Gurrola et al, 1994;Shi et al, 2020), all borrowing slightly from exploration seismology, where velocity spectral analysis is used to disentangle phases, given a known earth model (O. Yilmaz, 1987).…”