Novel anisotropic teleseismic body-wave tomography code AniTomo to illuminate heterogeneous anisotropic upper mantle: Part I — Theory and inversion tuning with realistic synthetic data

Considering only isotropic wave propagation and neglecting anisotropy in teleseismic tomography studies is a simplification obviously incongruous with current understanding of the mantle-lithosphere plate dynamics. Therefore, we have developed a code for anisotropicteleseismic tomography (AniTomo), which allows to invert relative traveltime residuals of teleseismic P waves simultaneously for coupled anisotropic-isotropic P-wave velocity models of the upper mantle. Due to a more complex anisotropic propagation of S waves, the AniTomo is applicable only to P-wave data. Weak hexagonal anisotropy together with isotropic velocity heterogeneities are interpreted as a cause of the observed P-wave traveltime residuals. Moreover, the axis of the hexagonal symmetry can be oriented freely in all directions, which represents a unique approach among recent approaches that usually incorporate only azimuthal or radial anisotropy into the body-wave tomography.