Abstract
The Pasisar seismic acquisition system combines a source at the sea surface and a deep-towed single channel streamer. This unconventional device geometry reduces the width of the first Fresnel zone which increases the lateral resolution. However, the device acquisition geometry generates artifacts on seismic profiles and induces large incidence angles of the seismic signal. A specific processing sequence must be applied to the data to obtain a readable seismic section. Penetration of the seismic signal depends on the energy of the signal reaching the seafloor and on its incidence angle. Because of smaller source energy, 800 Joules Sparker data cannot be acquired in water depth larger than 1500 m for example, whereas there is no depth limit for the use of this system with air gun sources. Differential acoustic absorption of seismic frequencies (below 1000 Hz) in the water column is negligible when compared with wave fronts expansion. Thus, the horizontal resolution of any seismic system strongly depends on the frequency spectrum of the seismic source and on the travel distances. Pasisar and conventional seismic profiles being usually simultaneously recorded, we illustrate the interest of using a hybrid seismic device by comparing horizontal resolutions as well as signal-to-noise ratio obtained with both the Pasisar and conventional systems. In addition, by carefully picking time arrivals of a reflection on simultaneously recorded surface and deep-towed seismic records, it is possible to estimate the average interval seismic velocity. We present the simplified example of a horizontal reflector.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Aki, K. and Richards, P. G., 1979, Quantitative Seismology, vol. I, W. H. Freeman and Co, San Francisco, 557 pp.
Bowen, A. N., 1984, A High Resolution Seismic Profiling System Using a Deep Towed Horizontal Hydrophone Streamer, Mar. Geophys. Res. 6, 275–293.
Claerbout, J. F., 1985, Imaging the Earth's Interior, Blackwell Scientific Publications, New York, 398 pp.
Fagot, M. G., 1983, Seabed 2 Program. A Deep-Towed Sound Source and Hydrophone Array System: Performance, Prediction Analysis and Hardware Description, in Pace M. (ed.), Acoustics and the Seabed, Bath Univ. Press, New York, pp. 369–377.
François, R. E. and Garrison, G. R., 1982, Sound Absorption Based on Ocean Measurements, Part II: Boric Acid Contribution and Equation for Total Absorption, J. Acoustic Soc. Am. 72, 1879–1890.
Hernandez, F., Marsset, B., Savoye, B., De Roeck, Y. H., Meunier, J., and Lopes, L., 1994, '94, 13- 16 Sept. 1994, Brest, France, II, pp. 665–670.
Mazé, J.-P., 1991, Faisabilité méthodologique du système sismique source au bateau/récepteur sur le SAR, Rapp. DEA, Aix-Marseille Univ., 40 pp.
Pascouet, A. P., 1991, Something New Under the Water, the Bubbleless Air Gun, The Leading Edge 10, 79–81.
Podevin, P. and Lecomte, I., 1991, Finite Difference Computation of Travel Times in Very Contrasted Velocity Models: A Massively Parallel Approach and Its Associated Tools, Geophys. J. I. 105, 271–284.
Savoye, B., Léon, P., De Roeck, Y. H., Marsset, B., Lopes, L., and Herveéou, J., 1995, Pasisar: A New Tool for Near-Bottom Very High Resolution Profiling in Deep Water, First Break 6, 253–258.
Sibuet, J.-C., Thomas, Y., Marsset, B., Nouzé, H., Louvel, V., Savoye, B., and Le Formal, J.-P., 1996, Detailed Relationship Between Tectonics Sedimentation from Pasisar Deep-Towed Seismic Data Acquired in the Iberia Abyssal Plain. Proc. ODP, Scientific Results, 149, College Station, TX (Ocean Drilling Program), pp. 649–657.
Ryan, W. B. F., Hsü, K. J., Cita, M. B., Dumitrica, P., Lort, J., Maync, W., Nesterolf, W. D., Pautot, G., Stradner, M., Wezel, F. C., 1973, Site 125, Initial Reports of the Deep Sea Drilling Project, Volume XIII, Washington (U.S. Government Printing Office), pp. 175–218.
Thomas, Y., Sibuet, J.-C., Nouzé, H., and Marsset, B., 1996, Étude détaillée de la structure d'un bloc basculé de la marge continentale de la Galice (Ouest-Ibérie) à l'aide de données sismiques acquises près du fond (système Pasisar): Conséquences sur la structuration de cette marge, Bull. Soc. Géol. France 167, 559–569.
Thomas, Y., 1995, Le système d'acquisition sismique près du fond Pasisar: Mise au point de la chaîne de traitement, Rapp. Ifremer DRO/GM, 95–22, Brest, 120 pp.
Yilmaz, O., 1987, Seismic Data Processing, Investigation in Geophysics, vol. 2, Society of Exploration Geophysicists, 512 pp.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Nouzé, H., Sibuet, JC., Savoye, B. et al. Pasisar: Performances of a High and Very High Resolution Hybrid Deep-Towed Seismic Device. Marine Geophysical Researches 19, 379–395 (1997). https://doi.org/10.1023/A:1004278219794
Issue Date:
DOI: https://doi.org/10.1023/A:1004278219794