气候变化领域集成服务门户(CCPortal): Lateral Variations of Shear-Wave Velocity in the D '' Layer Beneath the Indian-Eurasian Plate Collision Zone

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DOI	10.1029/2019GL086856
	Lateral Variations of Shear-Wave Velocity in the D '' Layer Beneath the Indian-Eurasian Plate Collision Zone
	Li, Guohui; Bai, Ling; Ritsema, Jeroen
通讯作者	Bai, L (通讯作者)
发表日期	2020
ISSN	0094-8276
EISSN	1944-8007
卷号	47 期号:6
英文摘要	Seismic tomography has demonstrated that the shear-wave velocity is relatively high over a 3,000-km wide region in the lowermost mantle beneath southern and eastern Asia. This seismic anomaly demarcates the current position of slab remnants that may have subducted in the Cretaceous. To further characterize the seismic structure at smaller scales, we measure 929 residual travel time differences (delta t) between the phases ScS and S using recordings of eight earthquakes beneath the Indian Ocean at stations from the Chinese Digital Seismic Network. We interpret variations of delta t up to 10 s as due to horizontal shear-velocity variations in D '' beneath northern India, Nepal, and southwestern China. The shear velocity can vary by as much as 7% over distances shorter than 300 km. Our observations provide additional observational evidence that compositional heterogeneity and possibly melt contribute to the seismic structure of the lower mantle characterized by long-term subduction and mantle downwelling. Plain Language Summary Seismic tomography indicates that the seismic wave speed is relatively high in the lowermost mantle (i.e., the D '' region) beneath regions, such as eastern Asia, influenced by subduction since the Mesozoic era. Our new analysis of the propagation time of shear-wave reflections off the outer core (i.e., the phase ScS) corroborates the result from seismic tomography that the shear velocity in D '' beneath eastern Asia is high overall. However, we also find that the shear velocity can vary by as much as 7% over distances shorter than 300 km within a region of D '' beneath northern India, Nepal, and southwestern China. This provides new evidence for the thermochemical nature of D '' beneath downwelling regions of the mantle.
关键词	LOWERMOST MANTLE BENEATH SEISMIC EVIDENCE POST-PEROVSKITE MODEL BASE ANISOTROPY DISCONTINUITY HETEROGENEITY TOMOGRAPHY INVERSION
英文关键词	D; Indian-Eurasian plate collision zone; 3-D synthetic waveform; ScS and S phases; compositional heterogeneity; long-term subduction
语种	英语
WOS研究方向	Geology
WOS类目	Geosciences, Multidisciplinary
WOS记录号	WOS:000529097700051
来源期刊	GEOPHYSICAL RESEARCH LETTERS
来源机构	中国科学院青藏高原研究所
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/259840
推荐引用方式 GB/T 7714	Li, Guohui,Bai, Ling,Ritsema, Jeroen. Lateral Variations of Shear-Wave Velocity in the D '' Layer Beneath the Indian-Eurasian Plate Collision Zone[J]. 中国科学院青藏高原研究所,2020,47(6).
APA	Li, Guohui,Bai, Ling,&Ritsema, Jeroen.(2020).Lateral Variations of Shear-Wave Velocity in the D '' Layer Beneath the Indian-Eurasian Plate Collision Zone.GEOPHYSICAL RESEARCH LETTERS,47(6).
MLA	Li, Guohui,et al."Lateral Variations of Shear-Wave Velocity in the D '' Layer Beneath the Indian-Eurasian Plate Collision Zone".GEOPHYSICAL RESEARCH LETTERS 47.6(2020).