Frequency dependent Lg attenuation in south‐central Alaska

Abstract

The characteristics of seismic energy attenuation are determined using high frequency Lg waves from 27 crustal earthquakes, in south‐central Alaska. Lg time‐domain amplitudes are measured in five pass‐bands and inverted to determine a frequency‐dependent quality factor, Q(f), model for south‐central Alaska. The inversion in this study yields the frequency‐dependent quality factor, in the form of a power law: Q(f)=Q0 fη = 220(±30) f0.66(±0.09) (0.75≤f≤12Hz). The results from this study are remarkably consistent with frequency dependent quality factor estimates, using local S‐wave coda, in south‐central Alaska. The consistency between S‐coda Q(f) and Lg Q(f) enables constraints to be placed on the mechanism of crustal attenuation in south‐central Alaska. For the range of frequencies considered in this study both scattering and intrinsic attenuation mechanisms likely play an equal role.