Travel-time anomalies in the mantle under the North Atlantic
Lateral heterogeneity exists in the Earth's mantle, and may result in seismic velocity anomalies up to several per cent. If convection cells and plumes extend down to the core, then these features may be associated with local inhomogeneities observed in the lower mantle. Published data for dire...
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1977
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fthighwire:oai:open-archive.highwire.org:gji:49/2/487 2023-05-15T17:31:09+02:00 Travel-time anomalies in the mantle under the North Atlantic Stewart, Ian C. F. 1977-05-01 00:00:00.0 text/html http://gji.oxfordjournals.org/cgi/content/short/49/2/487 https://doi.org/10.1111/j.1365-246X.1977.tb03718.x en eng Oxford University Press http://gji.oxfordjournals.org/cgi/content/short/49/2/487 http://dx.doi.org/10.1111/j.1365-246X.1977.tb03718.x Copyright (C) 1977, Oxford University Press Articles TEXT 1977 fthighwire https://doi.org/10.1111/j.1365-246X.1977.tb03718.x 2013-05-27T17:21:29Z Lateral heterogeneity exists in the Earth's mantle, and may result in seismic velocity anomalies up to several per cent. If convection cells and plumes extend down to the core, then these features may be associated with local inhomogeneities observed in the lower mantle. Published data for direct and core-reflected P -wave residuals are used to delineate velocity anomalies in the middle—lower mantle under the North Atlantic. Differential ( PcP – P ) residuals indicate travel-time anomalies near the core—mantle transition, and may be due to core topography or lateral variations in velocity. It is assumed that the anomalies occur near the midpoints of the ray paths. The main source of error in the data set may arise from phases which have been identified incorrectly. Hence trend-surfaces are fitted to the residual data to show only the large-scale trends in anomaly values, with wavelengths of the order of 1000 km. The Azores and Colorado hot spots occur in a region covered by the data. A possible interpretation of the trend maps is that an anomalous zone extends from a relatively fast region at the core boundary at 35° N, 50° W up to these hot spots, at about 30 degrees from the vertical. This may agree with the suggestion of Anderson that plumes are chemical rather than thermal in origin. If inclined plumes do exist, the deviation from the ideal vertical plume or convection cell boundary may imply that lateral shear or other distortion effects exist in the mantle. Text North Atlantic HighWire Press (Stanford University) Geophysical Journal International 49 2 487 497 |
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English |
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Articles Stewart, Ian C. F. Travel-time anomalies in the mantle under the North Atlantic |
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description |
Lateral heterogeneity exists in the Earth's mantle, and may result in seismic velocity anomalies up to several per cent. If convection cells and plumes extend down to the core, then these features may be associated with local inhomogeneities observed in the lower mantle. Published data for direct and core-reflected P -wave residuals are used to delineate velocity anomalies in the middle—lower mantle under the North Atlantic. Differential ( PcP – P ) residuals indicate travel-time anomalies near the core—mantle transition, and may be due to core topography or lateral variations in velocity. It is assumed that the anomalies occur near the midpoints of the ray paths. The main source of error in the data set may arise from phases which have been identified incorrectly. Hence trend-surfaces are fitted to the residual data to show only the large-scale trends in anomaly values, with wavelengths of the order of 1000 km. The Azores and Colorado hot spots occur in a region covered by the data. A possible interpretation of the trend maps is that an anomalous zone extends from a relatively fast region at the core boundary at 35° N, 50° W up to these hot spots, at about 30 degrees from the vertical. This may agree with the suggestion of Anderson that plumes are chemical rather than thermal in origin. If inclined plumes do exist, the deviation from the ideal vertical plume or convection cell boundary may imply that lateral shear or other distortion effects exist in the mantle. |
format |
Text |
author |
Stewart, Ian C. F. |
author_facet |
Stewart, Ian C. F. |
author_sort |
Stewart, Ian C. F. |
title |
Travel-time anomalies in the mantle under the North Atlantic |
title_short |
Travel-time anomalies in the mantle under the North Atlantic |
title_full |
Travel-time anomalies in the mantle under the North Atlantic |
title_fullStr |
Travel-time anomalies in the mantle under the North Atlantic |
title_full_unstemmed |
Travel-time anomalies in the mantle under the North Atlantic |
title_sort |
travel-time anomalies in the mantle under the north atlantic |
publisher |
Oxford University Press |
publishDate |
1977 |
url |
http://gji.oxfordjournals.org/cgi/content/short/49/2/487 https://doi.org/10.1111/j.1365-246X.1977.tb03718.x |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
http://gji.oxfordjournals.org/cgi/content/short/49/2/487 http://dx.doi.org/10.1111/j.1365-246X.1977.tb03718.x |
op_rights |
Copyright (C) 1977, Oxford University Press |
op_doi |
https://doi.org/10.1111/j.1365-246X.1977.tb03718.x |
container_title |
Geophysical Journal International |
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49 |
container_issue |
2 |
container_start_page |
487 |
op_container_end_page |
497 |
_version_ |
1766128490709516288 |