Ambient Noise Level and Site Characterization in Northern Egypt

Abstract

The characterization of the background seismic noise in any seismological network is an essential task for checking the performance of the recording stations. Hence, a funded project from Science and Technology Funding Authority (STDF) was awarded by the National Research Institute of Astronomy and Geophysics (NRIAG) in 2017 to detect the recording capabilities of the Egyptian National Seismological Network (ENSN), established after the Cairo Earthquake which occurred in Egypt on October 12, 1992. This article covers the first output of the project which shows the results of noise assessment for nine broadband stations located in northern Egypt. For a proper assessment of seismic data quality for a part of the ENSN network, the PASSCAL Quick Look Extended (PQLX) software was used, which is based on the calculation of power spectral density (PSD) and probability density function (PDF) for the background noise. The analysis covered almost one year of continuously recorded seismic data. The results show that some stations have very low detectability and higher noise level in some frequency bands which affects the recording of seismic events, while others show good performance. Complete site analysis for all stations was done to illustrate the present site response to be able to recommend whether to keep a station or to relocate it. To achieve this, the seismic noise data extracted from all stations of the considered zone was studied to determine the horizontal to vertical (H/V) spectral ratio method to study the amplification parameters of the recording site. The output of this study is useful for detecting operational problems in the northern part of the Egyptian seismological network and could be relevant for the reconfiguration and optimization of ENSN stations.