Modelling seismic anisotropy variations across the Hikurangi subduction margin, New Zealand

The influence of melt on seismic anisotropy is examined with different small-scale (tens of kilometres) analytical modelling approaches calculating anisotropy due to melt occurring in aligned inclusions, such as cracks or bands. The models confirm that small amounts (1-2%) of melt can account for the strong anisotropy required for the wedge region in the preferred large-scale model. Additionally, we show that aligned melt inclusions on the order of tens of meters can provide a suitable explanation for the observed weak trend towards decreasing delay times with higher filtering frequency for teleseismic phases and the differences in local and teleseismic fast polarisations, which both sample the highly anisotropic mantle wedge.