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DOI	10.1093/gji/ggae130
	Evidence for weak azimuthal anisotropy beneath the Kumaon-Garhwal Himalaya
	Devi, Arti; Roy, Sunil K.; Kanaujia, Jyotima; Kumar, M. Ravi
发表日期	2024
ISSN	0956-540X
EISSN	1365-246X
起始页码	237
结束页码	3
卷号	237 期号:3
英文摘要	This study attempts to interrogate the upper mantle deformation pattern beneath the Kumaon-Garhwal region, located in the western Himalaya, using shear wave splitting (SWS) analysis of core-refracted (XK(K)S) phases recorded at 53 broad-band stations. The fast polarization azimuths (FPAs) revealed by 338 well constrained measurements are dominantly clustered around ENE-WSW, with a few along the NE and E-W directions. The delay times vary from 0.2 to 1.4 s, with an average of 0.6 s that is smaller than that for the Indian shield (similar to 0.8 s), central and eastern Himalayas. The northern part of the lesser Himalaya shows a slightly smaller delay time compared to the southern part, which is attributed to the weakening of azimuthal anisotropy caused by the dipping of the Indian lithosphere. In order to understand the crustal contribution, its anisotropy is measured by analysing the splitting of Ps conversions from the Moho (Pms), akin to that of the XK(K)S phases. However, reliable results for crustal anisotropy could be obtained only at 10 stations. The average delay time due to crustal anisotropy is 0.47 s, with a variation from 0.2 to 0.9 s. Although the dominant period of Pms is smaller than that of SK(K)S, crustal anisotropy contributing to splitting of the latter phases cannot be ruled out. The orientation of FPAs obtained from Pms phases is found to be parallel or sub-parallel to those from XK(K)S phases, suggesting a similar deformation mechanism in the mid- to lower-crust and upper mantle. On the basis of FPAs derived from XK(K)S measurements, the Kumaon-Garhwal Himalaya (KGH) region can be divided into four subregions. In the western and eastern parts, the FPAs are mostly aligned along NE and ENE-WSW, and NE, respectively. In the central and south-eastern parts, their orientation is along ENE-WSW and NW, respectively. The strong ENE-WSW orientation in the central part could result from a slightly variable anisotropy in the crust to the upper part of the lithosphere or basal topography causing deflection of mantle flow. Also, the NW orientation in the south-eastern part of KGH is associated with a shallow source within the lithosphere. Application of the spatial coherency technique to single-layered anisotropic parameters results in a depth of 220-240 km, implying that the dominant source of anisotropy could lie in the upper mantle.
英文关键词	Asia; Body waves; Seismic anisotropy; Continental margins: convergent; Kinematics of crustal and mantle deformation
语种	英语
WOS研究方向	Geochemistry & Geophysics
WOS类目	Geochemistry & Geophysics
WOS记录号	WOS:001225926100002
来源期刊	GEOPHYSICAL JOURNAL INTERNATIONAL
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/306393
作者单位	Council of Scientific & Industrial Research (CSIR) - India; CSIR - National Geophysical Research Institute (NGRI); Academy of Scientific & Innovative Research (AcSIR)
推荐引用方式 GB/T 7714	Devi, Arti,Roy, Sunil K.,Kanaujia, Jyotima,et al. Evidence for weak azimuthal anisotropy beneath the Kumaon-Garhwal Himalaya[J],2024,237(3).
APA	Devi, Arti,Roy, Sunil K.,Kanaujia, Jyotima,&Kumar, M. Ravi.(2024).Evidence for weak azimuthal anisotropy beneath the Kumaon-Garhwal Himalaya.GEOPHYSICAL JOURNAL INTERNATIONAL,237(3).
MLA	Devi, Arti,et al."Evidence for weak azimuthal anisotropy beneath the Kumaon-Garhwal Himalaya".GEOPHYSICAL JOURNAL INTERNATIONAL 237.3(2024).