The Beam-Forming Technique for Enhancement of Noisy Seismic Refraction Data

Arewa James Ogah, Ani Donatus Chinedu

Kaduna Polytechnic.
Kogi State University.

DOI: 10.4236/ijg.2012.324087                

Abstract

We have described a method of obtaining useful information from noisy seismic refraction data. The simple method, tagged beam-forming technique, is based on the basic time-distance equations of refraction seismology. It involves basically of introducing relative time delays to individual seismic traces of seismic refraction spread to correct for the non-coincidence of the incidence seismic energy at different geophones, and averaging the traces to obtain the beam. The assumption here is that the signal is coherent between the geophones while the noise is random, and for groups of geophones corresponding to the same refraction segments of the travel time curve, this basic assumption is valid. The process of beam forming therefore leads to improvement in signal-to-noise ratio (SNR) and correct determination of the intercept times which are subsequently used to compute other geologic layer parameters. The ability of the applied technique to filter out or minimize random noise has been tested using a modified random number routine. The performance test on computation of geologic layer parameters using very noisy synthetic data reveals that the method is still very reliable even with very poor quality data having SNR as small as 0.05.

Keywords

Seismic Refraction; Beam-Forming; Filter; Random Noise

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	R. G. Anderson and G. A. McMechan, “Noise-Adaptive Filtering of Seismic Shot Records,” Geophysics, Vol. 53, No. 5, 1988, pp. 638-649.
[2]	M. Bekara and M. van der Baan, “Random and Coherent Noise Attenuation by Empirical Mode Decomposition,” Geophysics, Vol. 74, No. 5, 2009, pp. v89-v98.
[3]	G. Liu, X. Chen, J. Du and K. Wu, “Radom Noise Attenuation Using f-x Regularized Non-Stationary Auto- Regression,” Geophysics, Vol. 77, No. 2, 2012, pp. v61- v69.
[4]	W. M. Telford, L. P. Geldart and R. E. Sheriff, “Applied Geophysics,” 2nd Edition, Cambridge University Press, Cambridge, 1990.
[5]	A. D. Chinedu and I. B. Osazuwa, “Generalized Reciprocal Method Applied in Processing Seismic Refraction Data from the Basement Terrain of Zaria, North-Western Nigeria,” Nigerian Journal of Physics, Vol. 20, No. 2, 2008, pp. 377-385.
[6]	P. C. Ervin, L. D. McGinnis, R. M. Otis and K. C. Hall, “Automated Analysis of Marine Refraction Data, a Computer Algorithm,” Geophysics, Vol. 48, No. 5, 1989, pp. 582-589.
[7]	R. De Franco, “Multi-Refractor Imaging with Stacked Refraction Convolution Section,” Geophysical Prospecting, Vol. 53, No. 3, 2005, pp. 335-348. doi:10.1111/j.1365-2478.2005.00478.x
[8]	W. Lowrie, “Fundamentals of Geophysics,” Cambridge University Press, Cambridge, 1997.
[9]	M. J. Merchant, “The ABC’s of Fortran Programming,” Wadsworth Publishing Co., California, 1979.
[10]	D. Denham, “The Use of geophone Groups to Improve the Signal-to-Noise of the First Arrival in Refraction Shooting,” Geophysical Prospecting, Vol. 11, No. 4, 1963, pp. 389-395. doi:10.1111/j.1365-2478.1963.tb02044.x