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...
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Online Access: | https://doi.org/10.1016/j.epsl.2018.01.033 |
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ftcaltechauth:oai:authors.library.caltech.edu:v14wf-m4v37 2024-06-23T07:55:56+00:00 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 https://doi.org/10.1016/j.epsl.2018.01.033 unknown Elsevier https://doi.org/10.1016/j.epsl.2018.01.033 oai:authors.library.caltech.edu:v14wf-m4v37 eprintid:85441 resolverid:CaltechAUTHORS:20180327-075916427 info:eu-repo/semantics/openAccess Other Earth and Planetary Science Letters, 489, 267-276, (2018-05-01) near podal PcP precursor lowermost mantle small-scale heterogeneity info:eu-repo/semantics/article 2018 ftcaltechauth https://doi.org/10.1016/j.epsl.2018.01.033 2024-06-12T03:16:28Z 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. Received 29 August 2017, Revised 25 January 2018, Accepted 29 January 2018, Available online 14 March 2018. We thank the State Earthquake Information Service-Data Management Center of China, National Research Institute for Earth Science and Disaster Prevention of Japan, Incorporated Research Institutions for Seismology Data Management Center for providing data used in this study. Seismic Analysis Code (SAC) and Generic ... Article in Journal/Newspaper okhotsk sea Caltech Authors (California Institute of Technology) Okhotsk Earth and Planetary Science Letters 489 267 276 |
institution |
Open Polar |
collection |
Caltech Authors (California Institute of Technology) |
op_collection_id |
ftcaltechauth |
language |
unknown |
topic |
near podal PcP precursor lowermost mantle small-scale heterogeneity |
spellingShingle |
near podal PcP precursor lowermost mantle small-scale heterogeneity 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 |
topic_facet |
near podal PcP precursor lowermost mantle small-scale heterogeneity |
description |
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. Received 29 August 2017, Revised 25 January 2018, Accepted 29 January 2018, Available online 14 March 2018. We thank the State Earthquake Information Service-Data Management Center of China, National Research Institute for Earth Science and Disaster Prevention of Japan, Incorporated Research Institutions for Seismology Data Management Center for providing data used in this study. Seismic Analysis Code (SAC) and Generic ... |
format |
Article in Journal/Newspaper |
author |
Zhang, Baolong Ni, Sidao Sun, Daoyuan Shen, Zhichao Jackson, Jennifer M. Wu, Wenbo |
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://doi.org/10.1016/j.epsl.2018.01.033 |
geographic |
Okhotsk |
geographic_facet |
Okhotsk |
genre |
okhotsk sea |
genre_facet |
okhotsk sea |
op_source |
Earth and Planetary Science Letters, 489, 267-276, (2018-05-01) |
op_relation |
https://doi.org/10.1016/j.epsl.2018.01.033 oai:authors.library.caltech.edu:v14wf-m4v37 eprintid:85441 resolverid:CaltechAUTHORS:20180327-075916427 |
op_rights |
info:eu-repo/semantics/openAccess 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 |
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1802648735083134976 |