PAGEOPH, Vol. 134, No. 1 (1990) 0033-4553/90/010117-1751.50 + 0.20/0 9 1990 Birkh/iuser Verlag, Basel Joint Inversion of Travel Times and Waveforms by Means of Annealing Algorithms. Application to a Seismic Refraction Experiment X. LANA l and M. D. MARTINEZ l Abstract --An algorithm of annealing is applied to a joint inversion of travel times and waveforms belonging to a synthetically generated seismic refraction experiment. The medium (crust and upper mantle) is modelled by a set of plane stratified layers and a halfspace. The obtained structure (elastic parameters and depth of layers) shows that, in spite of contaminating seismic noise and poor knowledge of the seismic source, annealing methods are a good tool in these kinds of inversion problems. We think that many characteristics of the annealing process described here could be used with real data and more sophisticated media for the crust and upper mantle of the earth than the present example. Key words: Seismic refraction, travel times and waveforms joint inversion, annealing algorithms. Introduction The travel time inversion of seismic waves propagating in the crust and upper mantle of the earth, with the aim of improving the knowledge of the earth's interior, is currently a well established problem. A review of the methodology involved in such a problem can be found in TARANTOLA (1987a,b) IVANSSON (1987), FIRBAS (1987) and NOLET (1987), among others. The joint inversion of travel times and waveforms is another possibility which offers a better knowledge of the earth's interior than the former inversion, because of the dependence of the refraction and reflection coefficients modelling the wave- form on elastic parameters and densities of the medium. As a counterpart, due to the complicated dependence of the waveform on elastic parameters of the earth, the application of the usual inversion theory as in TARANTOLA (1987a,b) and NERCES- SIAN et al. (1984) among others, sometimes does not lead to reliable results. Taking into consideration that the elastic parameters minimizing some misfit function will be the solution of our inversion problem, the main objective will be to accurately 1 Departament de Fisica i Enginyeria Nuclear. Escola Trcnica Superior d'Enginyers Industrials de Barcelona. Universitat Politrcnica de Catalunya. Av. Diagonal, 647, 08028 Barcelona, Spain.