Abstract
AbstractSeismic body‐wave tomography studies typically assume an isotropic upper mantle, possibly mapping anisotropy into artificial isotropic velocity anomalies in the resulting images. The Eastern Mediterranean with its oceanic, continental, and extinct subduction systems, as well as dense station coverage, provides an ideal setting to explore this issue. To examine the influence of seismic anisotropy, our study deals with both synthetic and real data inversions in which realistic seismic anisotropy models derived from 3D mantle convection simulations and shear wave splitting measurements are taken as a priori constraints. Spatial large‐scale velocity perturbations are mostly consistent between models derived with and without considering anisotropy. Small differences in the magnitude (up to 2%) and shape of velocity perturbations occur, and some structures are less diffuse when including anisotropy. Additionally, good backazimuthal coverage of teleseismic events and a larger data set improve the resolution of our model with respect to previous tomography studies and allow us to better interpret first‐order isotropic velocity anomalies. Key features, such as the half‐arc subducting oceanic plate in the southern Aegean and a wide and deep tear in the slab beneath southwestern Turkey, are clearly visible in all models. Our final tomography images also provide evidence for a shallow horizontal tear in the northern Hellenides and a vertical tear between two parts of the Cyprian slab. In eastern Anatolia, slab‐related high‐velocity anomalies are absent due to the continental collision and break‐off.
Highlights
Seismic tomography is a well-established method that is frequently used to investigate upper mantle subduction tectonics and kinematics by constraining variations in seismic velocity.Over the last two decades, there have been many P and/or S wave tomography studies conducted to understand the complex tectonic setting beneath the Eastern Mediterranean region (e.g., Biryol et al, 2011; Blom et al, 2020; Çubuk-Sabuncu et al, 2017; Fichtner, Saygin, et al, 2013; Fichtner, Trampert, et al, 2013; Piromallo & Morelli, 2003; Portner et al, 2018) (Figure 1)
The modeling results are consistent with observations on seismic anisotropy, i.e., station averaged fast polarization directions (FPDs) primarily based on shear wave splitting (SWS) measurements, which indicate the presence of strong anisotropy evidenced by splitting time delays (TDs) of up to 2 s (e.g., Confal et al, 2016; Evangelidis et al, 2011; Paul et al, 2014)
We showed that anisotropy can affect velocity perturbations in some areas, with local differences of up to 2% compared to an isotropic tomography approach
Summary
Over the last two decades, there have been many P and/or S wave tomography studies conducted to understand the complex tectonic setting beneath the Eastern Mediterranean region (e.g., Biryol et al, 2011; Blom et al, 2020; Çubuk-Sabuncu et al, 2017; Fichtner, Saygin, et al, 2013; Fichtner, Trampert, et al, 2013; Piromallo & Morelli, 2003; Portner et al, 2018) (Figure 1) These studies employed different data sets, the resolved images of the lithosphere and asthenosphere have implied very similar features in the mantle such as subducting and fragmented slabs as well as hot upwelling material. This produces delayed arrival times that can be mapped by isotropic tomography into a low-velocity anomaly as shown by Bezada et al
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