THE APPLICATION OF BEAM-FORMING TECHNIQUE TO ENHANCE LOW QUALITY SEISMIC REFRACTION DATA
THE APPLICATION OF BEAM-FORMING TECHNIQUE TO ENHANCE LOW QUALITY SEISMIC REFRACTION DATA
| dc.contributor.author | OGAH, Arewa James | |
| dc.date.accessioned | 2014-02-27T14:32:00Z | |
| dc.date.available | 2014-02-27T14:32:00Z | |
| dc.date.issued | 1990-03 | |
| dc.description | Thesis submitted to the Postgraduate School, Ahmadu Bello University, in partial fulfillment of the requirements for the award of the degree of MASTER OF SCIENCE IN APPLIED GEOPHYSICS. Department of Physics Faculty of Science Ahmadu Bello University Zaria, Nigeria. March, 1990 | en_US |
| dc.description.abstract | The beam-forming (or delay and sum) method applied to refraction data involves steering of seismic arrivals from the same refractor for coherency, summing them and taking their average to obtain a 'master trace' called the beam. Based on the basic time-distance equations of refraction semismology, the technique achieves signal-to-noise ratio improvement in the process of forming the beam. Automatic determination of apparent layerivelocities was achieved by using ranges of trial velocities, and finding the velocity which maximizes the beam energy. Corresponding intercept times were determined by statistical estimation. A computer programme written to perform the beam-forming operation was tested on data consisting of noiseless synthetic data, noisy synthetic data, and real refraction data from the Kubanni Drainage Basin, Results with the syntetic data showed that errors in velocity determination varied from 0.67 - 4.20% for clean data to 1.00 - 6.00% for very noisy data; while for intercept times, corresponding errors were 0.01 - 3.00% and 5.00 - 24.00% respectively. Results from real data collected in the Kubanni basin revealed existence of two distinct geologic interfaces separating different rock units. P-wave velocity ranges of 527 - 700 m/s and 713 - 802 m/s correspond to different mixtures of silt, sand and savannah loam, and a mixture of weathered laterite and savannah loam respectively, which form the top layers at different locations. A range of 937 - 1870 m/s corresponds to a mixture of wet sand and clay that wholly or partly form the middle layer, while 2055 - 3663 m/s and 3810 - 4325 m/s correspond to weathered and fresh basements respectively. Correlation of the refraction results with water depths in some wells suggest that the Qquifers in the basin have P-wave velocity range of 1667 - 2417 m/s. The results also revealed that the basement depths vary between 12 m in some locations to 24m in others, and that the general direction of dip of the layers is toward the Kubanni river, although a local depression exists in the southern part of the project area. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/2921 | |
| dc.language.iso | en | en_US |
| dc.subject | APPLICATION, | en_US |
| dc.subject | BEAM-FORMING, | en_US |
| dc.subject | TECHNIQUE, | en_US |
| dc.subject | ENHANCE, | en_US |
| dc.subject | LOW QUALITY, | en_US |
| dc.subject | SEISMIC, | en_US |
| dc.subject | REFRACTION, | en_US |
| dc.subject | DATA. | en_US |
| dc.title | THE APPLICATION OF BEAM-FORMING TECHNIQUE TO ENHANCE LOW QUALITY SEISMIC REFRACTION DATA | en_US |
| dc.type | Thesis | en_US |