Lateral variations in the velocity of shear waves.

Observations of long period (>60 s) waveforms of seismic waves across the globe can be used to infer lateral variations in the velocity of shear waves. These variations are related to temperature and composition variations within the Earth’s deep interior. By applying highly accurate numerical wave propagation software, we have constrained velocity variations in the Earth’s uppermost 600 km with unprecedented resolution. The resulting model – SEMum – is available for download from here.