@article {
author = {Samaei, Meghdad and Miyajima, Masakatsu and Nojima, Nobuoto},
title = {Attenuation of Fourier spectra for 2012 Aharâ€“Varzaghan earthquakes, Northwestern Iran},
journal = {Journal of the Earth and Space Physics},
volume = {41},
number = {4},
pages = {23-38},
year = {2015},
publisher = {Institute of Geophysics, University of Tehran},
issn = {2538-371X},
eissn = {2538-3906},
doi = {10.22059/jesphys.2015.56029},
abstract = {In this research, we have used 102 strong motion recordings from 2012 Ahar-Varzaghan earthquakes (Mw=6.5 and Mw=6.3) to study the form of attenuation of shear wave Fourier amplitude spectra of those two events. The analysis is carried out in a broad-band frequency range from 0.1 to 20 Hz. A bilinear shape for geometrical spreading is assumed based on nonparametric regression of the data. The hinge point of the bilinear shape is around 60 km away from the earthquake source; the geometric spreading forms for the first and second segments are R-0.9 and R-0.5, respectively. The results of this study show that there is considerable dependency of the rate of geometrical spreading on frequency. If only frequencies above 1 Hz are considered, the first segment of geometrical spreading will have a slope steeper than R-1. In contract, for lower frequencies it has a gentle slope. The associated quality factor for the assumed shape of geometrical spreading (appropriate for frequencies logarithmically spaced between 0.1 to 20 Hz) is Q(f)=148 f 0.62. The estimated Q(f) in this study agrees well with the other estimated shear wave quality factors in the region; however, if the whole attenuation model (consisted of geometrical spreading and quality factor) is considered, there will be conspicuous differences between different models.},
keywords = {Ahar-Varzaghan earthquakes,Attenuation,Fourier spectra,Geometrical spreading,Northwestern Iran,quality factor},
title_fa = {Attenuation of Fourier spectra for 2012 Aharâ€“Varzaghan earthquakes, Northwestern Iran},
abstract_fa = {In this research, we have used 102 strong motion recordings from 2012 Ahar-Varzaghan earthquakes (Mw=6.5 and Mw=6.3) to study the form of attenuation of shear wave Fourier amplitude spectra of those two events. The analysis is carried out in a broad-band frequency range from 0.1 to 20 Hz. A bilinear shape for geometrical spreading is assumed based on nonparametric regression of the data. The hinge point of the bilinear shape is around 60 km away from the earthquake source; the geometric spreading forms for the first and second segments are R-0.9 and R-0.5, respectively. The results of this study show that there is considerable dependency of the rate of geometrical spreading on frequency. If only frequencies above 1 Hz are considered, the first segment of geometrical spreading will have a slope steeper than R-1. In contract, for lower frequencies it has a gentle slope. The associated quality factor for the assumed shape of geometrical spreading (appropriate for frequencies logarithmically spaced between 0.1 to 20 Hz) is Q(f)=148 f 0.62. The estimated Q(f) in this study agrees well with the other estimated shear wave quality factors in the region; however, if the whole attenuation model (consisted of geometrical spreading and quality factor) is considered, there will be conspicuous differences between different models.},
keywords_fa = {Ahar-Varzaghan earthquakes,Attenuation,Fourier spectra,Geometrical spreading,Northwestern Iran,quality factor},
url = {https://jesphys.ut.ac.ir/article_56029.html},
eprint = {https://jesphys.ut.ac.ir/article_56029_a5b68556855166cb70a4ddb97739ef52.pdf}
}