Crustal anisotropy beneath southeastern Tibet inferred from directional dependence of receiver functions

Ashwani Kant Tiwari, Arun Singh*, Dipankar Saikia, Chandrani Singh, Tuna Eken

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Özet

The present study reveals depth-dependent crustal anisotropic signatures beneath southeastern Tibet. It is used to characterize the rheology of major faults and shear zones, which is important for understanding crustal deformation and geodynamic processes beneath the study area. The depth-dependent anisotropic orientations have been investigated based on the directional dependence of radial and tangential receiver functions (RFs). To achieve our objective, we first computed 3683 good-quality P-RFs from 174 teleseismic earthquakes (M ≥ 5.5) recorded within epicentral distance range of 30 to 90 at 70 seismic stations of the Eastern Syntaxis experiment (XE Network). After that, we employed the harmonic decomposition technique at each seismic station to retrieve the first (k = 0), second (k = 1) and third (k = 2) degree harmonics from the RF dataset. Our study characterizes the type (horizontal or plunging) of the symmetry axis. The anisotropic axes of the upper crust (0–20 km) appear to vary from approximately N-S to NE-SW. They are usually orthogonal to orientations of major faults and suture zones in the region, implying the effect of structure-induced anisotropy. It can be explained by regularly oriented cracks or macroscopic structure alignment along the major faults. The anisotropic orientations of the middle crust (20–40 km) are NE-SW to E-W direction, reflecting a different pattern than those estimated in the upper crust. The lower crustal (40–70 km) anisotropic pattern (E-W or ESE-WNW direction) exhibits distinct orientations than the upper and middle crust. The crystal preferred orientations (CPO) of the mica and amphibole minerals are likely to cause anisotropy observed at mid-to-lower crustal depth ranges, emphasizing the role of ductile deformation due to material movement towards the east underneath southeastern Tibet. Our results, along with S(K)KS and direct S-waves splitting signatures, suggest mid-to-lower crust and lithospheric mantle material movement towards the east, while the discrepancies in anisotropic symmetric axes directions may be indicative for the partial coupling between the crust and upper mantle beneath the region.

Orijinal dilİngilizce
Makale numarası106912
DergiPhysics of the Earth and Planetary Interiors
Hacim331
DOI'lar
Yayın durumuYayınlandı - Eki 2022

Bibliyografik not

Publisher Copyright:
© 2022

Finansman

The IRIS data management center, Prof. Anne Meltzer and Project team of Namche Barwa Seismic Network (PASSCAL) are gratefully acknowledged for making the seismic data available. The figures are made using the Generic Mapping Tools software ( Wessel and Smith, 1998 ). This work has been performed under a scientific project of the Ministry of Earth Sciences, Govt. of India (MoES/P·O/Seismo/1(318)/2017(SDH)). Tuna Eken acknowledges financial support from Alexander von Humboldt Foundation (AvH) towards computational and peripheral resources. We would also like to thank editor Ana Ferreira and one anonymous reviewer for their invaluable feedback that have significantly improved the manuscript. The IRIS data management center, Prof. Anne Meltzer and Project team of Namche Barwa Seismic Network (PASSCAL) are gratefully acknowledged for making the seismic data available. The figures are made using the Generic Mapping Tools software (Wessel and Smith, 1998). This work has been performed under a scientific project of the Ministry of Earth Sciences, Govt. of India (MoES/P·O/Seismo/1(318)/2017(SDH)). Tuna Eken acknowledges financial support from Alexander von Humboldt Foundation (AvH) towards computational and peripheral resources. We would also like to thank editor Ana Ferreira and one anonymous reviewer for their invaluable feedback that have significantly improved the manuscript.

FinansörlerFinansör numarası
SDH
Alexander von Humboldt-Stiftung
Ministry of Earth SciencesMoES/P·O/Seismo/1(318)/2017

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