Treffer: Computation of Low Velocity Layer Correction Parameters by Computer Models.

Near-surface low velocity layer is a critical zone in seismic reflection surveys because shots fired within this zone tend to yield lowfrequency data, as the loose dirt does not transmit high frequencies adequately causing time delay to rays passing through it, thereby obscuring the reflection records. A computer program was designed in Visual Basic Computer programming language to carry out computation of low-velocity layer correction parameters used in statics computation and to determine energy source drilling depth. Such analysis by computer program minimizes slowness, time wastage and make results more reliable. The method of analysis used includes: Algorithms design and Visual Basic codes generation, employing the Least-Squares approximation, stepwise multi-linear regression, computing velocities from the reciprocals of the slopes of the lines and determining thickness for multi-layer cases. The program was debugged and test-run on Microsoft Windows using a set of thirty near-surface seismic velocity data acquired by seismic refraction technique within the South-Central Niger Delta. Based on the sampling density of thirty (30) refraction surveys, the average consolidated layer velocity of the area is 1790m/s, the weathered layer has a velocity gradient of 8.4(m/s)/m and an average velocity of 337m/s. The shot drilling depth is 3.7m in order to remove the effect of the low velocity surface layer and reduces all reflection times to a common height datum. The easy and quick nature of implementation and the closeness of the result to those of other researchers on the weathered layer in the Niger Delta indicate that the program, FAJSEIS is a reliable measure for the analysis of the near-surface seismic data [ABSTRACT FROM AUTHOR]

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