Influence of Upper Mantle Anisotropy on Isotropic P-Wave Tomography Images Obtained in the Eastern Mediterranean Region

Judith M. Confal, Maximiliano J. Bezada, Tuna Eken, Manuele Faccenda, Erdinc Saygin, Tuncay Taymaz

Research output: Contribution to journalArticlepeer-review

Abstract

Seismic 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.

Original languageEnglish (US)
Article numbere2019JB018559
JournalJournal of Geophysical Research: Solid Earth
Volume125
Issue number8
DOIs
StatePublished - Aug 1 2020

Bibliographical note

Funding Information:
This is an outcome of an ongoing PhD thesis by Judith M. Confal at the Graduate School of Istanbul Technical University (Turkey) supervised by Tuncay Taymaz. This study is funded by the National Scientific and Technological Research Council of Turkey (T?B?TAK), project no: ?AYDAG-115Y248. Furthermore, Judith M. Confal has been awarded a year long scholarship from the German Academic Exchange Service (DAAD, Jahresstipendien f?r Doktorandinnen und Doktoranden Studienjahr 2017/18) with the reference number 91671753. We are thankful to the University of Minnesota, Minneapolis, USA, for supporting the research, with the permission for the use of their servers and a study visit. We thank the Turkish Academy of Sciences (T?BA) in the framework for Young Scientist Award Program (T?BA-GEB?P) and the Alexander von Humboldt Foundation Research Fellowship Award for financial support and for further providing computing facilities and other relevant resources through Humboldt-Stiftung Follow-Up Programme. We would like to thank the Editor Martha Savage, Associate Editor Sebastien Chevrot, Anne Paul and an anonymous reviewer. Their constructive advice, suggestions, and judicial reviews improved this study immensely. We gratefully thank Caroline Johnson for reviewing an earlier version of the manuscript.

Keywords

  • Eastern Mediterranean
  • seismic anisotropy
  • seismic tomography
  • subduction tectonics
  • upper mantle

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