Three dimensional (3D) seismic survey was acquired and processed in Bornu-Chad basin, Nigeria with the aim of detecting and attenuating multiples to aid proper imaging of the subsurface. The 25.5km2 volume was processed using SeisUp processing software on a 32-Node Cluster Infrastructure (CI) hardware. Considering the imaging objectives and depth of interest of 1.2s-4.5s, the minimum, middle and maximum offsets were set at 500-2300m, 2500-4300m and 4500-7300m respectively. Since the study area comprised of dry open land and swampy Lake Chad, vibroseis and dynamite sources were used respectively. Charge depth was 0m (surface) for vibroseis and 25m dynamite. The dataset was first pre-conditioned, normalized, regularized before application of demultiple process. The detection and demultiple processes based on multiple characteristics of periodicity and velocity discrimination were applied as the multiples have comparable velocity with the primaries. The near-surface reverberations and short-period multiples were attenuated using predictive deconvolution and radon transform algorithms. High resolution radon was performed on post-migrated common-mid-point (CMP) gathers and stacked with 1kmx1km target line velocities. Internal multiples were detected and attenuated using data-driven methodology of extended internal multiple prediction (XIMP). Multiples detected were short, long period and interbed multiples on all frequencies ranges of 0 -90Hz but useful seismic frequency range was between 20Hz and 70Hz. The frequencies and amplitudes of the primaries and multiples were very comparable, therefore great care was taken in the attenuation processes. The results of this work has produced better seismic section for interpretation of subsurface geology in the study area.

Ambient noise was analysed from a two-dimensional (2D) seismic data acquired in the Middle Benue Trough, Nigeria for the purpose of characterizing the ambient seismic noise. Sercel 428XL recording instrument was deployed on 3 traverse lines where dynamite explosive sources and geophone detectors were used. The acquired data was processed using frequency wavenumber (FK) and wild amplitude attenuation (WAA) algorithms. The dominant amplitude of the primary reflection ranges between -20dB and -10dB, while those of the ambient seismic noise varies between -42dB and -3dB. The primary reflections have dominant frequency varying from 6Hz to 75Hz while that of ambient seismic noise varies between 4Hz and 70Hz. Analysis of the noise shows two distinct ground roll modes with velocities between 400 ms -1 and 810 ms -1 both of which are dispersive with wavelength (λ) of 61.5m and peak frequency at 6.5Hz. Analysis of passive noise records acquired showed that ambient seismic (background) noise level excluding source-generated noise average of 91.56% are below 25µV, which is the tolerance noise level limit. The combination of frequency wavenumber FK and WAA filters effectively attenuated the surface waves especially ground rolls and other high amplitude noise making the primary reflection very visible and better enhanced. The filtered amplitude values estimated from signal-to-noise (SNR) analysis using cross correlation (XC) method are much higher than the values of the unfiltered amplitudes indicating that SNR are highest when noises are attenuated from the data than when noise algorithm is not applied to the data. The attributes of these seismic noises will provide further information and solution for their suppression during seismic data acquisition and processing.