Quantification of Small-Scale Heterogeneity at the Core–Mantle Boundary Using Sample Entropy of SKS and SPdKS Synthetic Waveforms

Qualitative and quantitative analysis of seismic waveforms sensitive to the core–mantle boundary (CMB) region reveal presence ultralow-velocity zones (ULVZs) that have a strong decrease in compressional (P) shear (S) wave velocity, an increase density within thin structures. However, understanding their physical origin relation other large-scale structures lowermost mantle are limited due incomplete mapping ULVZs at CMB. The SKS SPdKS is routinely used infer ULVZ presence, but has thus far only been epicentral distance range. As SKS/SPdKS wavefield interacts with it generates additional arrivals, increasing complexity recorded wavefield. Here, we explore utilization multi-scale sample entropy method search for We investigate feasibility this approach through synthetic seismograms computed PREM, 1-, 2.5-, 3-D as well heterogeneous velocity 1- 2.5-D. find technique may be useful across wide range distances from 100° 130°. Such analysis, when applied real waveforms, could provide coverage roughly 85% by surface area