GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.3 GNGTS 2024 Fig. 2 - True P-wave (top two panels) and S-wave isotropic anomalies and fast symmetry axis orientatons for the three modeled tectonic setngs as predicted by micro-scale geodynamics modeling. Horizontal and E-W vertcal cross sectons (along the equatorial plane of the geodynamic model spherical domain) are shown. Velocity anomalies are computed (i) using the average of the three principal velocites, that for an hexagonally symmetric medium with a fast symmetry axis are , and (ii) with respect to reference radial velocity profles taken at the corner of the computatonal domain with minimum the X-Z axes coordinates, which is representatve of the far-feld, unperturbed mantle. The P-wave low velocity and S-wave high velocity anomalies at 150 km in the ridge model, and the P-wave high velocity and S-wave low velocity anomalies in the subducton model mantle wedge, are caused by deviatons from the hexagonally symmetry model. The length of the ellipses major axis is proportonal to: . The orientaton of the fast symmetry axis is parallel to the major axis of the ellipses, while the length of minor axis is proportonal to the dip relatve to the cross secton. ∆ l nV P , S V fast , V slow , V slow 2 f ( % ) = ( V fast − V slow ) ( V fast + V slow ) * 200 %