New comprehensive standard seismic noise models and 3D seismic noise variation for Morocco territory, North Africa, obtained using seismic broadband stations
Younes El Fellah 1 4 Abd El-Aziz Khairy Abd El-Aal 2 Mimoun Harnafi 1 Antonio Villaseñor 31 Earth Sciences Department, Scientific Institute, Mohammed V- University, Rabat 10106, Morocco.
2 Seismology Department, National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt.
3 Earth Sciences Department, Jaume Almera Institute, CSIC, Barcelona E-08028, Spain.
4 Corresponding author. Email: el.fellah.younes@gmail.com
Exploration Geophysics 48(3) 272-283 https://doi.org/10.1071/EG15053
Submitted: 10 June 2015 Accepted: 5 April 2016 Published: 20 May 2016
Abstract
In the current work, we constructed new comprehensive standard seismic noise models and 3D temporal-spatial seismic noise level cubes for Morocco in north-west Africa to be used for seismological and engineering purposes. Indeed, the original global standard seismic noise models published by Peterson (1993) and their following updates by Astiz and Creager (1995), Ekström (2001) and Berger et al. (2003) had no contributing seismic stations deployed in North Africa. Consequently, this preliminary study was conducted to shed light on seismic noise levels specific to north-west Africa. For this purpose, 23 broadband seismic stations recently installed in different structural domains throughout Morocco are used to study the nature and characteristics of seismic noise and to create seismic noise models for Morocco. Continuous data recorded during 2009, 2010 and 2011 were processed and analysed to construct these new noise models and 3D noise levels from all stations. We compared the Peterson new high-noise model (NHNM) and low-noise model (NLNM) with the Moroccan high-noise model (MHNM) and low-noise model (MLNM). These new noise models are comparable to the United States Geological Survey (USGS) models in the short period band; however, in the period range 1.2 s to 1000 s for MLNM and 10 s to 1000 s for MHNM display significant variations. This variation is attributed to differences in the nature of seismic noise sources that dominate Morocco in these period bands. The results of this study have a new perception about permanent seismic noise models for this spectacular region and can be considered a significant contribution because it supplements the Peterson models and can also be used to site future permanent seismic stations in Morocco.
Key words: Moroccan low-noise model (MLNM), new low-noise model (NLNM), overlay spectrum, seismic noise level, United States Geological Survey (USGS).
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