How P‐Wave Scattering Throughout the Entire Mantle Mimics the High‐Frequency Pdiff and Its Coda.

We document the arrival of seismic energy in the core shadow zone up to large distances beyond 150° more than 100 s prior to the core phases. Numerical simulations of the energy transport in an established heterogeneity model show that scattering throughout the entire mantle explains these observations. Diffraction at the core‐mantle boundary is unlikely in our 1–2 Hz frequency band and is not required indicating misleading terminology with reference to Pdiff for the scattered P∗P‐energy. Records of the largest deep earthquakes at low‐noise stations are key to the observation of the faint precursory signal which changes appearance with increasing distance from a coda‐like decay over a constant amplitude level around 130° to an emergent wave train. According to our simulations, different depth layers in the mantle dominate different time‐distance windows of the scattered wave train, providing the opportunity to improve the depth resolution of mantle heterogeneity models. Plain Language Summary: Earthquakes producing different types of waves that travel through the Earth help understand the structure of the Earth. We show that there is seismic energy arriving at stations in the shadow of the Earth's core more than 100 s before the waves usually considered the first arrivals. We used computer simulations to explain how this energy can travel so far in such a short time. Our results show that when there are heterogeneous structures distributed throughout the Earth's mantle the seismic energy can change direction at these structures due to a phenomenon called scattering. This allows the seismic energy to travel in the fast mantle material around the slow Earth's core. Previously, seismologists thought that part of this energy travels along the boundary between core and mantle by a process called diffraction. Our study provides a more elegant explanation for the observed energy and offers new possibilities for the investigation of Earth's structure. Key Points: We present observations of high‐frequency Pdiff coda more than 100 s before the core phases even at large distances beyond 150°Seismic energy simulations in published models of Earth's mantle heterogeneity show that scattered energy explains Pdiff and its codaDifferent‐depth mantle layers contribute to different time‐distance windows of the Pdiff coda benefiting imaging the mantle heterogeneity [ABSTRACT FROM AUTHOR]