UTILISATION D'UN CENTRAL DE DIGITALISATION D'ENREGISTREMENTS SISMIQUES*

Until such time as digital seismic recording techniques are in widespread use in the field and partly because it cannot afford digital equipment, C.E.P. has decided to build a processing system which can digitize and process seismic information in analog form on magnetic tapes.

C.E.P. was prompted to adopt the digital technique to enable it to proceed with its stratigraphical investigations, starting with the elaboration of synthetic records and followed by the study of signals and deconvolution.

Though the analog form of recording is not too suitable for digital processing owing to its low dynamic range, it seemed to us that it was nevertheless perfectly feasible to enhance the analog information by processing it digitally through an automatic computer.

This approach to the problem of data enhancement is more satisfactory than the (conventional) analog method, which is more complicated and less accurate.

• The digital processing system comprises:
• a magnetic playback system
• a two‐channel reproduction device
• an analog‐digital converter
• a 1620 IBM computer
• an automatic plotting device for graphical presentation of results.

Examples of different processing forms are presented:

• cancellation of A.G.C. action
• computation of seismic signal
• deconvolution
• correlation techniques
• anti‐singing
• study of the response of the various items of equipment.

We have come to the conclusion that very interesting results have been obtained in spite of the low dynamic range of the analog tapes.

With this equipment it is possible to study and process the data in digital form and compare results with those obtained by analog processing. Also, the experience gained will be very useful when digital field crews start operating.

Unfortunately, it is not possible for the time being to operate the equipment on a commercial production basis, but only to develop working methods, to conduct short studies or to guide and control analog processing techniques.

At present our efforts are therefore aimed at shortening the time required for processing and plotting.