Short Wavelength Topography on the Inner Core Boundary
International audience Constraining the topography of the inner core boundary (ICB) is important for studies of core-mantle coupling and the generation of the geodynamo. We present evidence for significant temporal variability in the amplitude of the inner core reflected phase PKiKP for an exception...
Main Authors: | , , |
---|---|
Other Authors: | , , , |
Format: | Conference Object |
Language: | English |
Published: |
HAL CCSD
2006
|
Subjects: | |
Online Access: | https://hal.archives-ouvertes.fr/hal-01654216 |
id |
ftccsdartic:oai:HAL:hal-01654216v1 |
---|---|
record_format |
openpolar |
spelling |
ftccsdartic:oai:HAL:hal-01654216v1 2023-05-15T18:23:34+02:00 Short Wavelength Topography on the Inner Core Boundary Romanowicz, Barbara Cao, Aimin Masson, Yder J. Seismological Laboratory Berkeley Department of Earth and Planetary Science UC Berkeley (EPS) University of California Berkeley (UC Berkeley) University of California (UC)-University of California (UC) San Francisco, United States 2006-12-11 https://hal.archives-ouvertes.fr/hal-01654216 en eng HAL CCSD hal-01654216 https://hal.archives-ouvertes.fr/hal-01654216 American Geophysical Union, Fall Meeting 2006 https://hal.archives-ouvertes.fr/hal-01654216 American Geophysical Union, Fall Meeting 2006, Dec 2006, San Francisco, United States [SDU]Sciences of the Universe [physics] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] info:eu-repo/semantics/conferenceObject Conference papers 2006 ftccsdartic 2022-12-04T01:40:39Z International audience Constraining the topography of the inner core boundary (ICB) is important for studies of core-mantle coupling and the generation of the geodynamo. We present evidence for significant temporal variability in the amplitude of the inner core reflected phase PKiKP for an exceptionally high quality earthquake doublet, which occurred in the South Sandwich Islands within a ten year interval (1993/2003). This doublet was observed post-critically at the short period Yellowknife seismic array (YK). The analysis of PKIKP/PKiKP amplitude ratios indicates that the PKiKP phases for the 1993 event - but not the 2003 event - are significantly defocused by structure near the inner core boundary (ICB). This observation cannot be explained by small differences in the eearthquake source, interference with another local, regional or teleseismic event, or different scattering from local heterogeneities near the stations or the sources. Combined with data from several other doublets, we infer the presence of topography at the inner- core boundary, with a horizontal wavelength of about 10 km. Such topography could be sustained by small scale convection at the top of the inner core, and is compatible with a rate of super-rotation of the inner core of ~0.1-0.15 deg/year. In the absence of inner core rotation, decadal scale temporal changes in the ICB topography would provide an upper bound on the viscosity at the top of the inner core. Conference Object South Sandwich Islands Yellowknife Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) Doublets ENVELOPE(98.667,98.667,-66.417,-66.417) Sandwich Islands South Sandwich Islands Yellowknife |
institution |
Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
English |
topic |
[SDU]Sciences of the Universe [physics] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] |
spellingShingle |
[SDU]Sciences of the Universe [physics] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] Romanowicz, Barbara Cao, Aimin Masson, Yder J. Short Wavelength Topography on the Inner Core Boundary |
topic_facet |
[SDU]Sciences of the Universe [physics] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] |
description |
International audience Constraining the topography of the inner core boundary (ICB) is important for studies of core-mantle coupling and the generation of the geodynamo. We present evidence for significant temporal variability in the amplitude of the inner core reflected phase PKiKP for an exceptionally high quality earthquake doublet, which occurred in the South Sandwich Islands within a ten year interval (1993/2003). This doublet was observed post-critically at the short period Yellowknife seismic array (YK). The analysis of PKIKP/PKiKP amplitude ratios indicates that the PKiKP phases for the 1993 event - but not the 2003 event - are significantly defocused by structure near the inner core boundary (ICB). This observation cannot be explained by small differences in the eearthquake source, interference with another local, regional or teleseismic event, or different scattering from local heterogeneities near the stations or the sources. Combined with data from several other doublets, we infer the presence of topography at the inner- core boundary, with a horizontal wavelength of about 10 km. Such topography could be sustained by small scale convection at the top of the inner core, and is compatible with a rate of super-rotation of the inner core of ~0.1-0.15 deg/year. In the absence of inner core rotation, decadal scale temporal changes in the ICB topography would provide an upper bound on the viscosity at the top of the inner core. |
author2 |
Seismological Laboratory Berkeley Department of Earth and Planetary Science UC Berkeley (EPS) University of California Berkeley (UC Berkeley) University of California (UC)-University of California (UC) |
format |
Conference Object |
author |
Romanowicz, Barbara Cao, Aimin Masson, Yder J. |
author_facet |
Romanowicz, Barbara Cao, Aimin Masson, Yder J. |
author_sort |
Romanowicz, Barbara |
title |
Short Wavelength Topography on the Inner Core Boundary |
title_short |
Short Wavelength Topography on the Inner Core Boundary |
title_full |
Short Wavelength Topography on the Inner Core Boundary |
title_fullStr |
Short Wavelength Topography on the Inner Core Boundary |
title_full_unstemmed |
Short Wavelength Topography on the Inner Core Boundary |
title_sort |
short wavelength topography on the inner core boundary |
publisher |
HAL CCSD |
publishDate |
2006 |
url |
https://hal.archives-ouvertes.fr/hal-01654216 |
op_coverage |
San Francisco, United States |
long_lat |
ENVELOPE(98.667,98.667,-66.417,-66.417) |
geographic |
Doublets Sandwich Islands South Sandwich Islands Yellowknife |
geographic_facet |
Doublets Sandwich Islands South Sandwich Islands Yellowknife |
genre |
South Sandwich Islands Yellowknife |
genre_facet |
South Sandwich Islands Yellowknife |
op_source |
American Geophysical Union, Fall Meeting 2006 https://hal.archives-ouvertes.fr/hal-01654216 American Geophysical Union, Fall Meeting 2006, Dec 2006, San Francisco, United States |
op_relation |
hal-01654216 https://hal.archives-ouvertes.fr/hal-01654216 |
_version_ |
1766203591708639232 |