Investigating the Effect of Anisotropy on Isotropic Tomography Images of the Alboran Slab

A number of studies have concluded that seismic anisotropy can be mapped into artificial velocity anomalies by isotropic teleseismic body wave tomography inversion. Such artifacts can affect the interpretation of velocity models in terms of mantle processes. This is especially true for subduction zones, where the anisotropy field is often strong and complex. A recent study using synthetic data suggested that prescribing an estimate of the anisotropy field as an a-priori constraint on the tomography inversion may be a useful approach. We apply this approach to real data from the westernmost Mediterranean. Currently located between Spain and Morocco, the narrow Alboran slab has undergone significant rollback. This has resulted in the development of considerable lattice preferred orientation (and consequent seismic anisotropy) in the surrounding mantle; as evidenced by shear-wave splitting studies. We prescribe localized anisotropy consistent with shear-wave splitting results in order to investigate whether specific anomalies may be a product of unaccounted-for anisotropy. Our main target anomalies are large, low-velocity anomalies that surround the slab in recent teleseismic tomography images.