The usual methods of velocity calculation by correlation applied to borehole acoustic body waves may give results of poer quality, even in some homogeneous formations and without interference waves such as criss-crosses. It is the case of the deep crystalline borehole KTB (Windisehesehenbaeh, Germany) where the body waves (particularly the P waves) do not have simple shapes. In fact, two waves arrive successively at velocities faster than 5000 m/s, and then two other waves at velocities ranging between 3000 and 4000 m/s. In order to study their variations in relation to depth, we have performed a new automatic method of wave velocity calculation based upon the velocity of a chosen crest. This particular crest is selected by the software from the fust receiver signal according to a high relative amplitude criterion and it is then located on the signals of the seven following receivers (sce Fig.I). In the case of the KTB acoustic data, we can easily point out four crests as indicated on the example of Fig.1 Thus we calculate the seven velocities - with their standard deviation - of each "crest" using the time intervals between the first receiver and each of the seven other ones.


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