Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors
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 ten...
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ftcaltechauth:oai:authors.library.caltech.edu:85441 2023-05-15T17:52:41+02:00 Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors Zhang, Baolong Ni, Sidao Sun, Daoyuan Shen, Zhichao Jackson, Jennifer M. Wu, Wenbo 2018-05-01 application/msword https://authors.library.caltech.edu/85441/ https://authors.library.caltech.edu/85441/2/1-s2.0-S0012821X18300517-mmc1.docx https://resolver.caltech.edu/CaltechAUTHORS:20180327-075916427 en eng Elsevier https://authors.library.caltech.edu/85441/2/1-s2.0-S0012821X18300517-mmc1.docx Zhang, Baolong and Ni, Sidao and Sun, Daoyuan and Shen, Zhichao and Jackson, Jennifer M. and Wu, Wenbo (2018) Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors. Earth and Planetary Science Letters, 489 . pp. 267-276. ISSN 0012-821X. doi:10.1016/j.epsl.2018.01.033. https://resolver.caltech.edu/CaltechAUTHORS:20180327-075916427 <https://resolver.caltech.edu/CaltechAUTHORS:20180327-075916427> other Article PeerReviewed 2018 ftcaltechauth https://doi.org/10.1016/j.epsl.2018.01.033 2021-11-18T18:45:21Z 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. Article in Journal/Newspaper okhotsk sea Caltech Authors (California Institute of Technology) Okhotsk Earth and Planetary Science Letters 489 267 276 |
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Caltech Authors (California Institute of Technology) |
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English |
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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. |
format |
Article in Journal/Newspaper |
author |
Zhang, Baolong Ni, Sidao Sun, Daoyuan Shen, Zhichao Jackson, Jennifer M. Wu, Wenbo |
spellingShingle |
Zhang, Baolong Ni, Sidao Sun, Daoyuan Shen, Zhichao Jackson, Jennifer M. Wu, Wenbo Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors |
author_facet |
Zhang, Baolong Ni, Sidao Sun, Daoyuan Shen, Zhichao Jackson, Jennifer M. Wu, Wenbo |
author_sort |
Zhang, Baolong |
title |
Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors |
title_short |
Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors |
title_full |
Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors |
title_fullStr |
Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors |
title_full_unstemmed |
Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors |
title_sort |
constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal pcp precursors |
publisher |
Elsevier |
publishDate |
2018 |
url |
https://authors.library.caltech.edu/85441/ https://authors.library.caltech.edu/85441/2/1-s2.0-S0012821X18300517-mmc1.docx https://resolver.caltech.edu/CaltechAUTHORS:20180327-075916427 |
geographic |
Okhotsk |
geographic_facet |
Okhotsk |
genre |
okhotsk sea |
genre_facet |
okhotsk sea |
op_relation |
https://authors.library.caltech.edu/85441/2/1-s2.0-S0012821X18300517-mmc1.docx Zhang, Baolong and Ni, Sidao and Sun, Daoyuan and Shen, Zhichao and Jackson, Jennifer M. and Wu, Wenbo (2018) Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors. Earth and Planetary Science Letters, 489 . pp. 267-276. ISSN 0012-821X. doi:10.1016/j.epsl.2018.01.033. https://resolver.caltech.edu/CaltechAUTHORS:20180327-075916427 <https://resolver.caltech.edu/CaltechAUTHORS:20180327-075916427> |
op_rights |
other |
op_doi |
https://doi.org/10.1016/j.epsl.2018.01.033 |
container_title |
Earth and Planetary Science Letters |
container_volume |
489 |
container_start_page |
267 |
op_container_end_page |
276 |
_version_ |
1766160382613782528 |