Upper mantle dynamics of Bangladesh by splitting analysis of core-mantle refracted SKS, PKS, and SKKS phases

Ashwani Kant Tiwari; Kirti Bhushan; Tuna Eken; Arun Singh

doi:10.1016/j.pepi.2018.03.006

Upper mantle dynamics of Bangladesh by splitting analysis of core-mantle refracted SKS, PKS, and SKKS phases

Ashwani Kant Tiwari, Kirti Bhushan, Tuna Eken, Arun Singh^*

^*Corresponding author for this work

Department of Geophysical Engineering

Indian Institute of Technology Kharagpur

Research output: Contribution to journal › Article › peer-review

4 Citations (Scopus)

Abstract

New shear wave splitting measurements are obtained from the Bengal Basin using core-mantle refracted SKS, PKS, and SKKS phases. The splitting parameters, namely time delays (δt) and fast polarization directions (ϕ), were estimated through analysis of 54 high-quality waveforms (⩾2.5 signal to noise ratio) from 30 earthquakes with magnitude ⩾5.5 recorded at ten seismic stations deployed over Bangladesh. No evidence of splitting was found, which indicates azimuthal isotropy beneath the region. These null measurements can be explained by either vertically dipping anisotropic fast axes or by the presence of multiple horizontal anisotropic layers with different fast polarization directions, where the combined effect results in a null characterization. The anisotropic fabric preserved from rifting episodes of Antarctica and India, subduction-related dynamics of the Indo-Burmese convergence zone, and northward movement of the Indian plate creating shear at the base of the lithosphere can explain the observed null measurements. The combined effect of all these most likely results in a strong vertical anisotropic heterogeneity, creating the observed null results.

Original language	English
Pages (from-to)	21-32
Number of pages	12
Journal	Physics of the Earth and Planetary Interiors
Volume	279
DOIs	https://doi.org/10.1016/j.pepi.2018.03.006
Publication status	Published - Jun 2018

Bibliographical note

Publisher Copyright:
© 2018 Elsevier B.V.

Funding

The IRIS data management center and Project team of BanglaQuake seismic network are gratefully acknowledged for making the seismic data available. This work was performed under the project IAI, IITKGP funded by the Ministry of Earth Sciences Govt. of India. T. Eken acknowledges financial support from Alexander von Humboldt Foundation (AvH) towards computational and peripherals resources. We thank James Mechie and Derek Schutt for their help in proofreading of the manuscript. We thank the topical editor and two anonymous reviewers for their valuable comments and suggestions, which helped us to improve the paper substantially.

Funders	Funder number
Alexander von Humboldt-Stiftung
Ministry of Earth Sciences

Keywords

Bengal Basin
Null splitting measurements
Seismic azimuthal anisotropy
Shear wave splitting

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10.1016/j.pepi.2018.03.006

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title = "Upper mantle dynamics of Bangladesh by splitting analysis of core-mantle refracted SKS, PKS, and SKKS phases",

abstract = "New shear wave splitting measurements are obtained from the Bengal Basin using core-mantle refracted SKS, PKS, and SKKS phases. The splitting parameters, namely time delays (δt) and fast polarization directions (ϕ), were estimated through analysis of 54 high-quality waveforms (⩾2.5 signal to noise ratio) from 30 earthquakes with magnitude ⩾5.5 recorded at ten seismic stations deployed over Bangladesh. No evidence of splitting was found, which indicates azimuthal isotropy beneath the region. These null measurements can be explained by either vertically dipping anisotropic fast axes or by the presence of multiple horizontal anisotropic layers with different fast polarization directions, where the combined effect results in a null characterization. The anisotropic fabric preserved from rifting episodes of Antarctica and India, subduction-related dynamics of the Indo-Burmese convergence zone, and northward movement of the Indian plate creating shear at the base of the lithosphere can explain the observed null measurements. The combined effect of all these most likely results in a strong vertical anisotropic heterogeneity, creating the observed null results.",

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AU - Tiwari, Ashwani Kant

AU - Bhushan, Kirti

AU - Eken, Tuna

AU - Singh, Arun

PY - 2018/6

Y1 - 2018/6

N2 - New shear wave splitting measurements are obtained from the Bengal Basin using core-mantle refracted SKS, PKS, and SKKS phases. The splitting parameters, namely time delays (δt) and fast polarization directions (ϕ), were estimated through analysis of 54 high-quality waveforms (⩾2.5 signal to noise ratio) from 30 earthquakes with magnitude ⩾5.5 recorded at ten seismic stations deployed over Bangladesh. No evidence of splitting was found, which indicates azimuthal isotropy beneath the region. These null measurements can be explained by either vertically dipping anisotropic fast axes or by the presence of multiple horizontal anisotropic layers with different fast polarization directions, where the combined effect results in a null characterization. The anisotropic fabric preserved from rifting episodes of Antarctica and India, subduction-related dynamics of the Indo-Burmese convergence zone, and northward movement of the Indian plate creating shear at the base of the lithosphere can explain the observed null measurements. The combined effect of all these most likely results in a strong vertical anisotropic heterogeneity, creating the observed null results.

AB - New shear wave splitting measurements are obtained from the Bengal Basin using core-mantle refracted SKS, PKS, and SKKS phases. The splitting parameters, namely time delays (δt) and fast polarization directions (ϕ), were estimated through analysis of 54 high-quality waveforms (⩾2.5 signal to noise ratio) from 30 earthquakes with magnitude ⩾5.5 recorded at ten seismic stations deployed over Bangladesh. No evidence of splitting was found, which indicates azimuthal isotropy beneath the region. These null measurements can be explained by either vertically dipping anisotropic fast axes or by the presence of multiple horizontal anisotropic layers with different fast polarization directions, where the combined effect results in a null characterization. The anisotropic fabric preserved from rifting episodes of Antarctica and India, subduction-related dynamics of the Indo-Burmese convergence zone, and northward movement of the Indian plate creating shear at the base of the lithosphere can explain the observed null measurements. The combined effect of all these most likely results in a strong vertical anisotropic heterogeneity, creating the observed null results.

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Upper mantle dynamics of Bangladesh by splitting analysis of core-mantle refracted SKS, PKS, and SKKS phases

Abstract

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Keywords

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