Dispersion Patterns Of Ground Roll (Seismic Noise) In Eastern Niger Delta

Abstract

Abstract Ground roll is a collection of surface waves generated by a seismic source. The vertical component of ground roll is composed of Raleigh waves. Raleigh waves have their most natural classification in terms of dispersion patterns. All seismic waves will exhibit dispersive character in a medium which displays attenuation and the most important cause of Raleigh wave dispersion is the presence of velocity layering. Results obtained during field seismic data acquisition with a Seismic crew of Geosource Nig Ltd has shown that the Niger Delta is not a homogeneous half-space but exhibits non-homogeneous character with unequal phase and group velocities. Hence the predominance of dispersive waves in the Niger Delta is due to its nonhomogeneous character. The complex topographic nature of the Niger Delta give rise to scattered Raleigh waves and these can be attenuated by use of field arrays that attenuates scattered Raleigh waves from all azimuths. Frequency - wavenumber transform of time-offset records can be interpreted in terms of Raleigh wave dispersion. This has been utilized in this study as dispersion curves of the ground roll in areas of study are presented and interpretation of ground roll dispersion patterns made with this. This study covers the "Uti" area of Akwa Ibom state in the eastern Niger Delta and is part of an ongoing study on a more effective characterisation of ground roll in that area. Results of this study will be very useful to seismologists, geophysicists, geologists, researchers and the academia who would like to know the ground roll properties and dispersion patterns in the Eastern Niger Delta with a view to designing attenuation strategies for it.