Seismic investigation of upper mantle structure

Due to the important role which the seismic discontinuities play in the understanding of the dynamics and evolution of the Earth, the number of studies dealing with this topic is enormous. Some studies focus on the regional fine-scale structure of the discontinuities to study more localized features and regional differences on a small scale. Others investigate the global structure of the discontinuities to study, for example, global convection patterns in the mantle, i.e. the up- and downwellings of the material.
In the next sections the most important methods are reviewed and the possibilities and restrictions of the different methods are discussed.