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Seismic Attenuation in the Middle America Region and the Frequency Dependence of Intrinsic Q

Luis A. Dominguez Ramirez, & Paul M. Davis

Published May 2013, SCEC Contribution #1644

We evaluate the separation of the different components of attenuation for the Middle America Region using an alternative form of the Multiple Lapse Time Widow (MLTW) method. By means of the comparison of the energy envelopes for three consecutive time windows after the S- wave arrival, we solve for the total attenuation Q^{-1}_{tot} and seismic albedo B_0 (ratio between the scattering to total attenuation) of the medium in the range of 1.0≤ f ≤15 Hz. Our analysis focuses on the separation of the individual components and the incorporation of the contribution of the leakage of energy into the mantle to the standard MLTW method.
We test the effect of variable geometric spreading, depth dependent scattering, and forward and back scattering operators. We conclude that adding a leakage term fits the data best, and reconciles our observations with laboratory experiments which suggest that intrinsic attenuation is roughly constant in the range of 1≤ f ≤10Hz and of the order of Q^{-1}_{Int}~1/1000. For the Middle America region, we find that Q_i ≈2000.

Citation
Dominguez Ramirez, L. A., & Davis, P. M. (2013). Seismic Attenuation in the Middle America Region and the Frequency Dependence of Intrinsic Q. Journal of Geophysical Research, 118(5), 2164-2175. doi: 10.1002/jgrb.50163.