We would like to know more about the initial incident wave and the transmitted wave on both sides of the crack. To achieve this, it is necessary to carry out a velocity correction which allows us to flatten or align the initial incident wave (which has a good signal to noise ratio). The correction velocity is chosen in a manner which allows us to obtain a maximum of the trace sum of the incident wave. Then a SVD filter (Filtering by singular value decomposition SVD) is applied separately to the incident and transmitted waves. The initial incident wave is not perfectly aligned, so it is necessary to sum 2 eigensections to correctly extract the required wave. Fluctuations in arrival time of the incident wave are due to a lack of precision in receiver locations. We note that the wavelet 's form of the transmitted wave has been greatly modified by its passage through the crack.