Influence of melt viscosity of basaltic and andesitic composition on seismic attenuation in partially molten gabbronorite

The characteristic frequencies at which two different melt-related attenuation mechanisms occur in partially molten gabbronorite are computed as a function of aspect ratios of the melt-filled cracks, and the melt viscosity. The computations were done for basaltic and andesitic melts. The melt viscosity is constrained by (i) laboratory measurements performed in the range 108–1014 Pa s with a creep apparatus and in the range 10−1 to 105 Pa s with a rotational Couette viscometer, and (ii) modeling of viscosity at high temperatures. The results of the characteristic frequency calculations suggest that melt squirt flow is a viable attenuation mechanism at seismic frequencies for aspect ratio of melt inclusions in the range 10−3 to 10−2 for the andesite, and 10−4 to 10−3 for the two basalts.