The influence of the North Anatolian Fault and a fragmenting slab architecture on upper mantle seismic anisotropy in the eastern Mediterranean
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
The eastern Mediterranean hosts, within the span of a few hundred kilometers, extensional, strike-slip, and collision tectonics above a set of fragmenting subducting slabs. Slab roll-back, toroidal flow, and lithospheric dripping/delamination processes are also believed to be operating. Associated asthenospheric flow and lithospheric de formation are expected to manifest as seismic anisotropy, measurable via study of SKS shear wave splitting. Surprisingly, previous SKS splitting investigations have resolved only long wavelength patterns of anisotropy in the region, interpreting them as large scale asthenospheric flow; moreover, no anisotropic signature has been associated with the North Anatolian Fault (NAF), unlike other major strike-slip plate boundaries world wide. We present a 29-year record of SKS splitting observations, revealing hitherto unrecognized short-length-scale variations in anisotropy, and backazimuthal variations of splitting parameters that attest to multi-layered anisotropy. Lithospheric anisotropy beneath the NAF exhibits fast directions either fault-parallel or intermediate between the principle extensional strain rate axis and fault strike, diagnostic of a relatively low strained transcurrent mantle shear zone. Elsewhere, anisotropy is consistent with as thenospheric flow through tomographically-imaged slab gaps, and driven by Hellenic trench retreat. Evidence for westward flow of asthenosphere driving Anatolian plate motion is lacking. Shorter splitting delay times and nulls in central Anatolia suggest weaker azimuthal anisotropy in the asthenosphere, supporting models that invoke ver tical mantle flow patterns (lithospheric dripping/asthenospheric upwelling). Thus, we conclude that the signal of mantle anisotropy more closely reflects the lithospheric de formation, complex slab architecture and geodynamic diversity of the region than pre36 viously recognized.
Date Issued
2021-09
Date Acceptance
2021-07-26
Citation
G3: Geochemistry, Geophysics, Geosystems: an electronic journal of the earth sciences, 2021, 22 (9), pp.1-26
ISSN
1525-2027
Publisher
American Geophysical Union
Start Page
1
End Page
26
Journal / Book Title
G3: Geochemistry, Geophysics, Geosystems: an electronic journal of the earth sciences
Volume
22
Issue
9
Copyright Statement
© 2021. The Authors.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Sponsor
Natural Environment Research Council
Identifier
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GC009896
Grant Number
NE/L002515/1
Subjects
Geochemistry & Geophysics
02 Physical Sciences
04 Earth Sciences
Publication Status
Published
Date Publish Online
2021-08-23