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فیزیک زمین و فضا، جلد ۴۱، شماره ۴، صفحات ۲۳-۳۸
عنوان فارسی Attenuation of Fourier spectra for ۲۰۱۲ Ahar–Varzaghan earthquakes, Northwestern Iran
چکیده فارسی مقاله 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.
کلیدواژه‌های فارسی مقاله Ahar-Varzaghan earthquakes، Attenuation، Fourier spectra، Geometrical spreading، Northwestern Iran، quality factor،
عنوان انگلیسی Attenuation of Fourier spectra for 2012 Ahar–Varzaghan earthquakes, Northwestern Iran
چکیده انگلیسی مقاله 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.
کلیدواژه‌های انگلیسی مقاله Ahar-Varzaghan earthquakes, Attenuation, Fourier spectra, Geometrical spreading, Northwestern Iran, quality factor
نویسندگان مقاله مقداد سمایی |
postdoctoral researcher, graduate school of natural science and technology, kanazawa university, kanazawa, japan

masakatsu miyajima |
professor, graduate school of natural science and technology, kanazawa university, kanazawa, japan

nobuoto nojima |
professor, department of civil engineering, gifu university, gifu, japan

نشانی اینترنتی https://jesphys.ut.ac.ir/article_56029_a5b68556855166cb70a4ddb97739ef52.pdf
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