Abstract
<jats:p> Seismic attenuation provides complementary information to seismic velocity to constrain the mantle thermal and compositional conditions. Yet, quantitative interpretations of both seismic observables are limited. In this study, we first present 3-D apparent bulk and shear attenuation models beneath the Alaska Peninsula by jointly inverting P- and S-wave spectral decay and using a transdimensional Bayesian tomography method. The mantle wedge shows moderate apparent bulk attenuation and high shear attenuation with pronounced along-arc variations. We then semi-quantitatively interpret shear-wave velocity (V <jats:sub>S</jats:sub> ) and shear attenuation (Qs <jats:sup>-1</jats:sup> ) using a laboratory-based anelastic model. Low V <jats:sub>S</jats:sub> and low Qs <jats:sup>-1</jats:sup> are observed in the fore-arc mantle, reflecting low temperature and probably serpentinization. The low V <jats:sub>S</jats:sub> and elevated Qs <jats:sup>-1</jats:sup> across the mantle wedge indicate the combination of supersolidus temperature and the presence of partial melts. Furthermore, very high Qs <jats:sup>-1</jats:sup> and normal V <jats:sub>S</jats:sub> in the mantle wedge cannot be explained by grain-boundary sliding alone, invoking additional attenuation mechanisms. </jats:p>