next up previous contents
Home: Berkeley Seismological Laboratory
Next: Investigating Earth's Lower Mantle Up: Ongoing Research Previous: Direct Inversion of Mode

Frequency Dependent Anelasticity

Joseph Durek, Barbara Romanowicz


Anelasticity, and the resulting velocity dispersion, is required in the Earth to reconcile seismic observations spanning three decades in frequency [e.g. Montagner and Kennett, 1996) and to compare high-frequency laboratory measurements with low-frequency tomographic models [e.g. Romanowicz, 1990; Karato, 1994]. Observed seismic wave attenuation is well explained by frequency independent anelasticity, which led to the concept of the mantle response as a superposition of absorption peaks with roughly constant attenuation in the seismic band.

We have performed preliminary investigations of the frequency dependence of anelasticity using the tranverse component surface (T>80s) and body (T>32s) waveforms of Li and Romanowicz [1986] as well as a compilation of published normal mode quality factors. We consider a power law dependence of attenuation, $Q^{-1} \sim \omega^{-\alpha}$. In our preliminary investigation, we conclude:


Durek, J.J., and B. Romanowicz, Frequency Dependent Relaxation in the Seismic Band (invited abstract), EOS Trans. AGU, 78, 1997.

Dziewonski, A. M., and D. L. Anderson, Preliminary reference Earth model(PREM), Phys. Earth Planet. Inter., 25, 297-356, 1981.

Karato, S.,Importance of anelasticity in the interpretation of seismic tomography, Geophys. Res. Lett., 20,1623-1626, 1993.

Li, X.-D., and B. Romanowicz,Global mantle shear velocity model developed usingnonlinear asymptotic coupling theory,J. Geophys. Res., 101, 22,245-22,272, 1996.

Romanowicz, B., The upper mantle degree 2: Constraints and inferencesfrom global mantle wave attenuation measurements, J. Geophys. Res.,95, 11,051-11,071, 1990.

Romanowicz, B., C. Megnin, and X.-D. Li, Waveform inversion for global mantle elastic and anelastic structure (abstract), EOS Trans. AGU, 77, 482, 1996.

next up previous contents
Next: Investigating Earth's Lower Mantle Up: Ongoing Research Previous: Direct Inversion of Mode

The Berkeley Seismological Laboratory, 202 McCone Hall, UC Berkeley, Berkeley CA 94720
Questions and comments to
Copyright 1999, The Regents of the University of California.