Current Research on Geography, Earth Science and Environment Vol. 7

Nigeria is not located in regions with frequent incidences of earthquakes; however, recent occurrences of low to medium magnitude earthquakes required a robust seismicity monitoring in the country for seismic risk mitigation. Nigeria is presently expanding its critical facilities to meet the demands of the ever-increasing population. Hence, the evaluation of the performance of the Broadband Seismic Stations in Nigeria has become imperative. This study, therefore, aims to test the recording capability, data quality for research, and estimation of the signal-to-noise ratios of the stations. The methodology involved the noise analysis for the Kaduna station located in the basement complex in the northern part of Nigeria, and the Nsukka station on the sedimentary basin in the South, using the Pascal Quick Look Extended (PQLX) package, since Nigeria lies on the two predominant geology foundation. In the first instance, data used in the research were continuously recorded during 2010 for 1 year. Power spectral densities were computed from one-hour-long data segments from both stations. Secondly, possible sources of noise to the stations, as well as their signal-to-noise ratios (SNR), were estimated. The first and second approaches were compared with the global noise models of Peterson’s. Thirdly, data from both stations were tested for research reliability using noise correlation and receiver function techniques. The results showed high noise levels at both stations; low SNR at Nsukka and high SNR at Kaduna. Noise levels exceeded the high-noise model at periods >10 s at Kaduna, while Nsukka was dominated by noise at <1 s, with interstation spacing of 77–574 km preventing reliable tomography. Findings also showed that sources of noise to the stations are both natural and anthropogenic in nature. Results from noise correlations and receiver functions indicated that the correlations are antisymmetric, indicating that the noise sources are non-uniform. The seasonal variations of the noise were also observed in the monthly correlations. The receiver functions computed from the Nsukka station did not provide a sufficient number of receiver functions. There was no clear Moho conversion at Kaduna station, and the results of the H-K stack were poor. This study is intended to serve as a reference to illuminate operational impediments associated with broadband stations in Nigeria and suggest measures to improve data quality for healthy research. Future work should prioritise improved station installation and insulation, accurate instrument orientation and levelling, and replacement of short-period sensors with long-period sensors to enhance SNR and data quality.