Extended Data Figure 4 : Linear resolution analysis, examining recovery of synthetic whole- and partial-mantle plumes of width 1,000 km beneath Hawaii and Iceland.

From: Broad plumes rooted at the base of the Earth's mantle beneath major hotspots

Extended Data Figure 4

Synthetic plume input models, shown in the upper row of panels, have a peak amplitude of −2% and a cosine-cap lateral amplitude profile (thus, the effective width above 1% anomaly strength is only 500 km). In addition to looking at a whole-mantle plume, we also examine recovery of plumes truncated at successively greater depths (1,000 km, 1,500 km and 2,000 km) to assess vertical smearing. Artefacts seen above the truncation depth in the synthetic input models are due to slight aliasing phenomena associated with the radial b-spline basis functions used to parameterize our model. We find that all four input plumes are recovered quite well beneath both Hawaii (centre row), with relatively denser data coverage, and Iceland (bottom row), with comparatively sparser coverage—although there is a slight difference in amplitude recovery beneath the two (maximum amplitude recovered is shown for each panel). Importantly, we see no evidence of lateral (or, in the case of the truncated plumes, radial) smearing, nor do we detect significant gaps in recovery. However, recovered amplitude does vary as a function of depth, with comparatively weaker, although still satisfactory, recovery in the less well sampled mid-mantle (of the order of half of the input anomaly strength). For a more thorough discussion of the caveats implied by linear resolution analysis in the context of our inversion, as well as additional resolution tests, see ref. 4.