A New Probe Into the Innermost Inner Core Anisotropy via the Global Coda‐Correlation Wavefield

Investigations of the Earth's inner core (IC) using seismic body waves are limited by their volumetric sampling due to uneven global distribution large earthquakes and receivers. The sparse coverage IC leads uncertainties in its anisotropy, directional dependence velocity. Yet, detailed constraints on such as magnitude, spatial distribution, required understand crystallographic structure IC's iron solidification deformation processes. Here, we present a new method investigate anisotropic properties based coda-correlation wavefield constructed from late coda earthquakes. We perform comprehensive travel time analysis I2*, an IC-sensitive correlation feature identified counterpart direct wavefield's PKIKPPKIKP waves, yet fundamentally different. Namely, I2* is mathematical manifestation similarity among specific phases with same slowness detected correlograms short inter-receiver distance range. Our overcomes shortage paths sensitive central volume, also known innermost (IMIC). observed I2*’s variations relative rotation axis (ERA) support model cylindrical anisotropy 3.3% strength zonal pattern slow oriented 55° ERA. thus find compelling evidence for deep distinct although cannot resolve depth at which change occurs. This finding reinforces previous inference IMIC, implications evolution.