Seismic waves generated by earthquakes and nuclear explosions are affected by material properties of the Earth, thus can be used to image its internal structure. Seismic imaging of the 3D structure of the Earth has revealed a great deal about the dynamics of the Earth's interior. Two approaches are generally employed: forward
modeling of selected data sets and inversion of large data sets. Here I'll show a few examples of our work on inner core anisotropy, inner core rotation, core-mantle boundary variation, and lithosphere structure and dynamics of the Tibetan Plateau.