Upper mantle anisotropy inferred from shear wave splitting beneath the Eastern Indian Shield region
We estimate the shear wave splitting parameters vis-à-vis the thicknesses of the continental lithosphere beneath the two permanent seismic broadband stations located at Dhanbad (DHN) and Bokaro (BOKR) in the Eastern Indian Shield region. Broadband seismic data of 146 and 131 teleseismic earthquake e...
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| Format: | Article |
| Language: | English |
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Elsevier
2018-11-01
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| Series: | Geoscience Frontiers |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S1674987117302128 |
| _version_ | 1797761731691282432 |
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| author | Kuntal Bhukta Prosanta K. Khan Prantik Mandal |
| author_facet | Kuntal Bhukta Prosanta K. Khan Prantik Mandal |
| author_sort | Kuntal Bhukta |
| collection | DOAJ |
| description | We estimate the shear wave splitting parameters vis-à-vis the thicknesses of the continental lithosphere beneath the two permanent seismic broadband stations located at Dhanbad (DHN) and Bokaro (BOKR) in the Eastern Indian Shield region. Broadband seismic data of 146 and 131 teleseismic earthquake events recorded at DHN and BOKR stations during 2007–2014 were analyzed for the present measurements. The study is carried out using rotation-correlation and transverse component minimization methods. We retain our “Good”, “Fair” and “Null” measurements, and estimate the splitting parameters using 13 “Good” results for DHN and 10 “Good” results for BOKR stations. The average splitting parameters (ϕ, δt) for DHN and BOKR stations are found to be 50.76°±5.46° and 0.82 ± 0.2 s and 56.30°±5.07° and 0.95 ± 0.17 s, and the estimated average thicknesses of the anisotropic layers beneath these two stations are ∼ 94 and ∼109 km, respectively. The measured deviation of azimuth of the fast axis direction (ϕ) from the absolute motion of the Indian plate ranges from ∼8° to 14°. The measured deviation of azimuth of the fast axis direction (ϕ) from the absolute motion of the Indian plate ranges from ∼8° to 14°. The eastward deviation of the fast axis azimuths from absolute plate motion direction is interpreted to be caused by induced outflow from the asthenosphere. Further, the delay time found in the present analysis is close to the global average for continental shield areas, and also coherent with other studies for Indian shield regions. The five “Null” results and the lower delay time of ∼0.5–0.6 s might be indicating multilayer anisotropy existing in the mantle lithosphere beneath the study area. Keywords: Eastern Indian shield, Seismic anisotropy, Splitting parameters, Absolute plate motion |
| first_indexed | 2024-03-12T19:18:16Z |
| format | Article |
| id | doaj.art-bc3981ae1e1b40c78bf2b5d8d5147873 |
| institution | Directory Open Access Journal |
| issn | 1674-9871 |
| language | English |
| last_indexed | 2024-03-12T19:18:16Z |
| publishDate | 2018-11-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Geoscience Frontiers |
| spelling | doaj.art-bc3981ae1e1b40c78bf2b5d8d51478732023-08-02T05:25:25ZengElsevierGeoscience Frontiers1674-98712018-11-019619111920Upper mantle anisotropy inferred from shear wave splitting beneath the Eastern Indian Shield regionKuntal Bhukta0Prosanta K. Khan1Prantik Mandal2Indian Institute of Technology (Indian School of Mines), Dhanbad, IndiaIndian Institute of Technology (Indian School of Mines), Dhanbad, India; Corresponding author.National Geophysical Research Institute, Hyderabad, IndiaWe estimate the shear wave splitting parameters vis-à-vis the thicknesses of the continental lithosphere beneath the two permanent seismic broadband stations located at Dhanbad (DHN) and Bokaro (BOKR) in the Eastern Indian Shield region. Broadband seismic data of 146 and 131 teleseismic earthquake events recorded at DHN and BOKR stations during 2007–2014 were analyzed for the present measurements. The study is carried out using rotation-correlation and transverse component minimization methods. We retain our “Good”, “Fair” and “Null” measurements, and estimate the splitting parameters using 13 “Good” results for DHN and 10 “Good” results for BOKR stations. The average splitting parameters (ϕ, δt) for DHN and BOKR stations are found to be 50.76°±5.46° and 0.82 ± 0.2 s and 56.30°±5.07° and 0.95 ± 0.17 s, and the estimated average thicknesses of the anisotropic layers beneath these two stations are ∼ 94 and ∼109 km, respectively. The measured deviation of azimuth of the fast axis direction (ϕ) from the absolute motion of the Indian plate ranges from ∼8° to 14°. The measured deviation of azimuth of the fast axis direction (ϕ) from the absolute motion of the Indian plate ranges from ∼8° to 14°. The eastward deviation of the fast axis azimuths from absolute plate motion direction is interpreted to be caused by induced outflow from the asthenosphere. Further, the delay time found in the present analysis is close to the global average for continental shield areas, and also coherent with other studies for Indian shield regions. The five “Null” results and the lower delay time of ∼0.5–0.6 s might be indicating multilayer anisotropy existing in the mantle lithosphere beneath the study area. Keywords: Eastern Indian shield, Seismic anisotropy, Splitting parameters, Absolute plate motionhttp://www.sciencedirect.com/science/article/pii/S1674987117302128 |
| spellingShingle | Kuntal Bhukta Prosanta K. Khan Prantik Mandal Upper mantle anisotropy inferred from shear wave splitting beneath the Eastern Indian Shield region Geoscience Frontiers |
| title | Upper mantle anisotropy inferred from shear wave splitting beneath the Eastern Indian Shield region |
| title_full | Upper mantle anisotropy inferred from shear wave splitting beneath the Eastern Indian Shield region |
| title_fullStr | Upper mantle anisotropy inferred from shear wave splitting beneath the Eastern Indian Shield region |
| title_full_unstemmed | Upper mantle anisotropy inferred from shear wave splitting beneath the Eastern Indian Shield region |
| title_short | Upper mantle anisotropy inferred from shear wave splitting beneath the Eastern Indian Shield region |
| title_sort | upper mantle anisotropy inferred from shear wave splitting beneath the eastern indian shield region |
| url | http://www.sciencedirect.com/science/article/pii/S1674987117302128 |
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