Fig. 2: Synthetic tests to compare the array-based coherent receiver function (CRF) method with the conventional receiver function (RF) method.

a The synthetic model based on the slab geometry in central Cascadia and the distribution of the broadband seismic stations (triangles) shown in Fig. 1b. Synthetic seismograms are generated for the specific source-receiver pairs (with the earthquakes located in the southeast direction in Supplementary Fig. 1) in central Cascadia to simulate real situations. b Conventional RF stacking images for noise-free synthetic data. In this scenario, only high-frequency (0.05–1.5 Hz) results are presented to highlight RF signals related to slab-related discontinuities. c, d Conventional RF stacking images for synthetic data with realistic noise. With low frequency (0.05–0.3 Hz), the slab-top and slab-Moho can be coherently identified only with their multiples, and it is difficult to recognize the slab-LAB. With high frequency (0.05–1.5 Hz), slab-related signals manifest as intermittent features. e, f Array-based CRF stacking images for synthetic data with realistic noise. The slab-top, slab-Moho, and slab-LAB can be resolved in both low- and high-frequency imaging. See Supplementary Fig. 7 for noise-free synthetic tests.