An analysis of core–mantle boundary Stoneley mode sensitivity and sources of uncertainty

SUMMARY Stoneley modes are a special subset of normal whose energy is confined along the core–mantle boundary (CMB). As such, they offer unique glimpse into Earth structure at base mantle. They often observed through coupling with mantle due to rotation, ellipticity and lateral heterogeneity, though can be detected without such coupling. In this study, we explore relative sensitivities seismic spectra two low-frequency several factors, taking as reference fully coupled computation up 3 mHz in model S20RTS. The factors considered (i) theoretical, by exploring extent which various approximations accurately reproduce (ii) model-based, how parameters CMB topography, attenuation S- P-wave structures, source solution may influence spectra. We find that mode-pair insufficiently accurate, but within range ±0.1 produces acceptable spectra, compared full This has important implications for splitting function measurements, computed under assumption isolated or best, group uncertainties velocity dominate other parameters. addition, also test hypothetical models density against real data. These tests indicate that, mode spectral data here, it difficult make any firm statement on whether large-low-shear-velocity-provinces denser lighter than their surroundings. conclude better constraints long wavelength elastic structure, particularly velocity, need obtained, before making further statements deep heterogeneity. particular, dense anomaly thin layer (less ∼100–200 km) not resolvable using tested while ability higher frequency resolve requires investigations.