Revealing fine layering within cratonic upper mantle using H-κ-φ anisotropic stacking with crust-corrections.

Seismic imaging with converted body waves has been used to infer layering within the globallithosphere leading to observations of a globally ubiquitous boundary known as themid-Lithosphere discontinuity (MLD). Explanatory models include partial melt/chemicalstratification, anisotropy, and elastically-accommodated grain-boundary sliding; each withunique implications for the geological evolution of continents. We present a new method forinvestigating these hypotheses, using a parametric approach which involves stacking ofthree-component earthquake-source deconvolved- receiver function traces.We conduct a statistical parameter search to determine the lithospheric discontinuity depth(H), the wave-speed ratio (κ), and order,φ, of harmonic back-azimuth variations, whichcan distinguish conversions from sub-crustal layers with anisotropic media. We demonstratethe procedure with a pilot study of synthetic waveforms and long-running seismic stationslocated in the Precambrian region of the US. We target sub-crustal depths, and distinguishbetween free surface reverberations, using a suite of high-resolution crustal 1D (PREM,IASP91, AK135) and 3D models (Crust1.0, LITHO1.0, and EMC-US.2016) velocity models.The results have important implications for the origin of the MLD and the approach can beused to study other cratonic regions globally. [ABSTRACT FROM AUTHOR]