Study of rock anelasticity for seismological application

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Recent experimental studies have shown that anelasticity of polycrystalline materials is subject to the Maxwell frequency (fm) scaling: 1/Q(fn) with fn=f/fm. However, the applicability of this scaling to the seismic waves has not been guaranteed because fn in the laboratory is usually much lower than that of the seismic waves (6 < log_10(fn) < 9). By using polycrystalline organic borneol as an analogue to mantle rock, we measured anelasticity up to log_10(fn) = 8 and found that this scaling is not fully applicable at log_10(fn) > 4. A closer examination showed that each of the relaxation spectra obtained under various temperature, grain size, and chemical composition can be represented by the superposition of a background subject to the Maxwell frequency scaling and a peak centered at log_10(fn) ~ 3. Significant increases of the peak amplitude and width with increasing temperature, drain size, and impurity content result in failure of the Maxwell frequency scaling at log_10(fn) > 4.