DOI: 10.1016/j.epsl.2018.01.033
Scopus记录号: 2-s2.0-85044020920
论文题名: Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors
作者: Zhang B. ; Ni S. ; Sun D. ; Shen Z. ; Jackson J.M. ; Wu W.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 489 起始页码: 267
结束页码: 276
语种: 英语
英文关键词: lowermost mantle
; near podal PcP precursor
; small-scale heterogeneity
Scopus关键词: Geology
; Mathematical models
; Complex mineral assemblage
; Functional forms
; Lowermost mantle
; near podal PcP precursor
; Small amplitude
; Small-scale heterogeneity
; Strong perturbations
; Synthetic seismogram
; Seismology
; amplitude
; coda
; computer simulation
; core-mantle boundary
; finite difference method
; heterogeneity
; lower mantle
; numerical model
; P-wave
; seismogram
; seismology
; wave scattering
; Central America
; China
; Myanmar
; Pacific Ocean
; Sea of Okhotsk
; South America
英文摘要: Volumetric heterogeneities on large (∼>1000 km) and intermediate scales (∼>100 km) in the lowermost mantle have been established with seismological approaches. However, there are controversies regarding the level of heterogeneity in the lowermost mantle at small scales (a few kilometers to tens of kilometers), with lower bound estimates ranging from 0.1% to a few percent. We take advantage of the small amplitude PcP waves at near podal distances (0–12°) to constrain the level of small-scale heterogeneity within 250 km above the CMB. First, we compute short period synthetic seismograms with a finite difference code for a series of volumetric heterogeneity models in the lowermost mantle, and find that PcP is not identifiable if the small-scale heterogeneity in the lowermost mantle is above 2.5%. We then use a functional form appropriate for coda decay to suppress P coda contamination. By comparing the corrected envelope of PcP and its precursors with synthetic seismograms, we find that perturbations of small-scale (∼8 km) heterogeneity in the lowermost mantle is ∼0.2–0.5% beneath regions of the China–Myanmar border area, Okhotsk Sea and South America. Whereas strong perturbations (∼1.0%) are found beneath Central America. In the regions studied, we find that this particular type of small-scale heterogeneity in the lowermost mantle is weak, yet there are some regions requiring heterogeneity up to 1.0%. Where scattering is stronger, such as under Central America, more chemically complex mineral assemblages may be present at the core–mantle boundary. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109970
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026, China; State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, 430077, China; Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125, United States; Department of Geosciences, Princeton University, Princeton, NJ 08544, United States
Recommended Citation:
Zhang B.,Ni S.,Sun D.,et al. Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors[J]. Earth and Planetary Science Letters,2018-01-01,489