"This proposal is meant to facilitate the transition of Prof. Auguste (Guust) Nolet from Princeton University back to Europe (Université de Nice/Sophia Antipolis). It addresses three aspects of his current research in global seismic tomography: 1. The merging of seismic data in different frequency ranges, including travel times and amplitudes of phases that do not satisfy the assumptions of geometrical optics ('finite-frequency tomography'), 2. Expanding the seismological data acquisition to the oceans by equiping underwater floats with hydrophones, 3. Incorporating wavelet expansions into the tomographic inversion. At a time that the first results from finite-frequency tomography are yielding very relevant results for an understanding of the Earth's chemical and thermal evolution, it is important that current research can be continued uninterrupted. The Marie Curie grant would enable active communication between researchers in the US and Europe with Nolet and his new students in France, and involve the oceanography group in Villefranche in the development of floats."