New body-wave time-delay database towards improving the seismic tomography of the lowermost mantle

A high-fidelity imaging of global mantle is fundamental and critical to improve the understanding about the dynamics of the Earth's interior. One decade ago, a database of time delays between ray predictions and observations was created for the S, SS and ScS waves and used to invert the SeisGlob2 mantle model. However, the lowermost part of the mantle, that has been convinced to be significantly heterogeneous and is closely related to the Large Low Shear Wave Province and Ultra Low Velocity Zones, is still poorly constrained. Utilizing the efficient parallel spectral element simulation code SPECFEM3D_GLOBE, we estimate the correlation time delays between seismic body phases in real seismograms and in synthetics, at seismic periods from 20 to 60 s. The effects of the crustal heterogeneity, topography/bathymetry and the flatness of Earth on the travel times of seismic waves, are well honoured in the 3D synthetics. Thus, we attribute the time delays dominantly to the 3D heterogeneities in the mantle. The increased number of stations in the past decade provides a better spatial coverage of observations. Another major advance of the new database is the incorporation of the Sdiff time delays, that contribute to a highly improved sampling of the global core-mantle boundary. We will present the new database with millions of estimates and the final inverted model.