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Upper crust attenuation in the Basin and Range Province of Sonora, Mexico

We estimated the S -wave quality factor Q ( f ) of the upper crust in northeastern Sonora, Mexico, using a two-layer model. The first layer of the model has a thickness of 1 km, and the frequency dependence of Q can be represented by the relation Q ( f ) = 127 f  0.7 in the frequency range of 0.5 ≤...

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Bibliographic Details
Published in:Journal of seismology 2021-10, Vol.25 (5), p.1241-1249
Main Authors: Castro, Raúl R., Villalobos-Escobar, Gina P.
Format: Article
Language:English
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Summary:We estimated the S -wave quality factor Q ( f ) of the upper crust in northeastern Sonora, Mexico, using a two-layer model. The first layer of the model has a thickness of 1 km, and the frequency dependence of Q can be represented by the relation Q ( f ) = 127 f  0.7 in the frequency range of 0.5 ≤ f ≤ 20 Hz. The second layer varies in depth between 1 and 21 km, and Q ( f ) = 181 f  0.7 in the same frequency range. The average Q of the model, weighted with the thickness of the layers, gives the relation Q ( f ) = 179.1 f  0.7 . We used nonparametric attenuation functions, determined in a previous study, to correct the observed spectral amplitudes, and then we retrieved source and site effects using a spectral inversion scheme. We used the resulting functions to separate source and site effects from the original spectral records and modeled Q for the 1-D model’s depths. We analyzed 38 local earthquakes recorded by 12 stations of the regional network RESNES ( Red Sísmica del Noreste de Sonora ). We found that the S -wave Q of the superficial layer is a factor of only 1.4 smaller than the more profound layer. This result validates the use of an average Q to correct spectral amplitudes by the effect of anelastic attenuation from waves traveling within the upper crust.
ISSN:1383-4649
1573-157X
DOI:10.1007/s10950-021-10025-0