A passive source Receiver Function experiment (REceiver FUnctions in the Central Andes) within the framework of the SFB 267 Deformation processes in the Andes across the entire Andes from the subduction zone in the west to the west-dipping inner crustal structure proposed under the eastern Altiplano along 21S. About 60 stations will be deployed along this profile for about two years. Experiences with earlier experiments have shown that such a long recording period is necessary because a sufficient number of high quality earthquakes must be recorded. A second