Seismic Background Noise Evaluation at Saki Seismic Station, Oyo State, Nigeria

Abstract

Measures have been taken to densify the seismic monitoring stations in Nigeria to enhance and supplement the monitoring and recording capacities of the current monitoring stations in the country, since local earthquakes are becoming more frequent. A comprehensive background noise analysis is advised to achieve peak performance and enhance comprehension of the new station's representative seismic signal. Determining the background noise for the recently installed seismic station at Saki in Oyo State to ensure the reliability of the data is the goal of this study. Using a MATLAB package, PQL, and Seisan software, the approach involves the collection of noise data from the station and processing it to determine and identify the appropriate background noise. The raw waveforms were sorted, de-trended, and demeaned to remove instrumental errors and other unwanted trends. The Fast Fourier Transform was implemented to convert the time series into the frequency domain to understand the behavior of the background noise at different frequency bands. The results show that the background noise on the three components of the Saki seismic station (Vertical (Z), horizontal (E), and northing (N)) was low on both low and high frequency bands, indicating a good station with low background noise.  The minimum and maximum amplitudes of the waveform and the number of counts also indicate a low background noise. The geology and location of the Saki seismic station may have contributed to the station's low-level and consistent background noise. The findings will assist in the comprehension of the potential background noise during the routine data processing, as well as serving as a benchmark for background noise analysis for future seismic stations in Nigeria.