The use of F-K filter in the elimination of artefacts from a shallow seismic reflection data in Zaria, Nigeria

Abstract

Near surface high resolution 2-D seismic reflection survey was carried out along the Zaria batholith. Zaria area forms part of the Precambrian basement complex of north central Nigeria which comprises Precambrian rocks made up of granite, gneiss and Low-grade metasediments. The granitic Zaria batholith intruded the gneiss and metasediments which forms the country rock. Reflection signals from shallow seismic survey in this area are often marred by surface waves, refraction and multiple reflections. The processing of the seismic data if not well handled often leads to migration artefacts which could be misconstrued as a seismic event. The field procedure employed for the geophysical survey was the split spread mode. The geophones were fixed at an interval of 1m, and a constant offset of 0.5 m. The common depth point method (CDP) with 12 fold coverage was adopted for the survey.
Several artefacts were noticed on the result of the seismic migrated section, when the fk filter was initially applied only on the pre-stacked seismic data. The filtering and the common midpoint stacking could not completely eliminate the seismic noise on the pre-stacked seismic data. However, when an fk filter was applied on the post-stacked seismic section, the remaining seismic noise that survives the initial processing flow was eliminated. When migration was carried out on the filtered post-stack seismic section, the resulting seismic section was free from artefacts, and
showed clear seismic events.

KEYWORDS: f-k filter, artefacts, shallow seismic, reflection, migration. Zaria