3:30 PM - 3:45 PM
[SIT04-02] Experimental study on polycrystal anelasticty with implications for upper mantle seismic structure
Keywords:anelasticity, seismic attenuation, upper mantle
The addition of impurity (diphenylamine) to borneol significantly reduces the melting (solidus) temperature from Tmelt = 477 K to Tmelt = 316 K. Therefore, we have speculated that the observed variation of the peak dissipation with impurity and temperature can be scaled by the normalized temperature T/Tmelt, such that the peak amplitude and width increase with increasing T/Tmelt. The significant broadening of the peak observed near (but below) the solidus temperature (T/Tmelt = 0.93) means that seismic velocity and Q are considerably lowered even without melt and has important implications for upper mantle seismic structure. We further investigated the detailed behavior of the peak dissipation at near solidus temperatures (0.88 ≤ T/Tmelt ≤ 1.01), and found that the peak amplitude saturates at about T/Tmelt = 0.95, but that the peak width continuously increases up to the supersolidus temperature T/Tmelt = 1.01. The obtained result was formulated in terms of the two nondimensional parameters f/fM and T/Tmelt and preliminarily applied to the seismic waves in the upper mantle. The result shows that low V and low Q occur at near solidus temperatures even without melt. At the onset of melting, seismic wave velocity shows a discrete reduction due to the poroelastic effect of melt, but the seismic attenuation does not show a discontinuous change.