TY - JOUR
ID - 56029
TI - Attenuation of Fourier spectra for 2012 Aharâ€“Varzaghan earthquakes, Northwestern Iran
JO - Journal of the Earth and Space Physics
JA - JESPHYS
LA - en
SN - 2538-371X
AU - Samaei, Meghdad
AU - Miyajima, Masakatsu
AU - Nojima, Nobuoto
AD - Postdoctoral Researcher, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan
AD - Professor, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan
AD - Professor, Department of Civil Engineering, Gifu University, Gifu, Japan
Y1 - 2015
PY - 2015
VL - 41
IS - 4
SP - 23
EP - 38
KW - Ahar-Varzaghan earthquakes
KW - Attenuation
KW - Fourier spectra
KW - Geometrical spreading
KW - Northwestern Iran
KW - quality factor
DO - 10.22059/jesphys.2015.56029
N2 - 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.
UR - https://jesphys.ut.ac.ir/article_56029.html
L1 - https://jesphys.ut.ac.ir/article_56029_a5b68556855166cb70a4ddb97739ef52.pdf
ER -