Determination of crystal orientation fabric from seismic wideangle data
It is known from ice core analyses that the crystal orientation fabric (COF) of ice sheets is anisotropic and changes over depth. A better understanding of these anisotropies as well as their remote detection is important to optimize flow models for ice. Here we show how seismic wideangle measuremen...
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Geophysical Research Abstracts Vol. 14, EGU2012-760, 2012 EGU General Assembly
2012
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ftawi:oai:epic.awi.de:26032 2024-09-15T17:42:06+00:00 Determination of crystal orientation fabric from seismic wideangle data Diez, Anja Eisen, Olaf Hofstede, Coen Bohlen, Thomas Weikusat, Ilka Kipfstuhl, Sepp 2012 application/pdf https://epic.awi.de/id/eprint/26032/ https://epic.awi.de/id/eprint/26032/1/EGU2012-760.pdf http://meetingorganizer.copernicus.org/EGU2012/EGU2012-760.pdf https://hdl.handle.net/10013/epic.39271 https://hdl.handle.net/10013/epic.39271.d001 unknown Geophysical Research Abstracts Vol. 14, EGU2012-760, 2012 EGU General Assembly https://epic.awi.de/id/eprint/26032/1/EGU2012-760.pdf https://hdl.handle.net/10013/epic.39271.d001 Diez, A. , Eisen, O. orcid:0000-0002-6380-962X , Hofstede, C. orcid:0000-0002-6015-6918 , Bohlen, T. , Weikusat, I. orcid:0000-0002-3023-6036 and Kipfstuhl, S. (2012) Determination of crystal orientation fabric from seismic wideangle data , EGU General Assembly, Vienna, 22 April 2012 - 27 April 2012 . hdl:10013/epic.39271 EPIC3EGU General Assembly, Vienna, 2012-04-22-2012-04-27Geophysical Research Abstracts Vol. 14, EGU2012-760, 2012 EGU General Assembly Conference notRev 2012 ftawi 2024-06-24T04:03:41Z It is known from ice core analyses that the crystal orientation fabric (COF) of ice sheets is anisotropic and changes over depth. A better understanding of these anisotropies as well as their remote detection is important to optimize flow models for ice. Here we show how seismic wideangle measurements can be used to determine the COF remotely. We demonstrate the principle formalism how observed seismic traveltimes can be related to COF properties by a forward model and then apply the formalism to field data. The eigenvalues that describe the ice fabric of the ice core EDML (Dronning Maud Land, Antarctca) are set into a relationship with the elasticity tensor. From the elasticity tensor the expected seismic velocities and reflection coefficients are calculated. Additionally we calculate the value eta from the Thomsen-parameters epsilon and delta. The value eta gives a measure of the anisotropy of vertical transverse isotropic (VTI)-media and is an important tool for the NMO-correction of anisotropic data. The approximation of reflection horizons as hyperbolas is not valid anymore in anisotropic media. The calculation of the moveout is therefore performed by a 4th order NMO-correction with the rms-velocity and the effective eta value as variables. This approach is applied to data from a wideangle survey shot at Halvfarryggen, Dronning Maud Land, Antarctica. From this data we derived rms-velocities and effective eta values. These values were than recalculated to interval velocities and interval eta values to give a hint on the measure of anisotropy of the different layers. The results give first insight into the anisotropies at Halvfarryggen. Conference Object Antarc* Antarctica Dronning Maud Land ice core Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) |
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Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) |
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description |
It is known from ice core analyses that the crystal orientation fabric (COF) of ice sheets is anisotropic and changes over depth. A better understanding of these anisotropies as well as their remote detection is important to optimize flow models for ice. Here we show how seismic wideangle measurements can be used to determine the COF remotely. We demonstrate the principle formalism how observed seismic traveltimes can be related to COF properties by a forward model and then apply the formalism to field data. The eigenvalues that describe the ice fabric of the ice core EDML (Dronning Maud Land, Antarctca) are set into a relationship with the elasticity tensor. From the elasticity tensor the expected seismic velocities and reflection coefficients are calculated. Additionally we calculate the value eta from the Thomsen-parameters epsilon and delta. The value eta gives a measure of the anisotropy of vertical transverse isotropic (VTI)-media and is an important tool for the NMO-correction of anisotropic data. The approximation of reflection horizons as hyperbolas is not valid anymore in anisotropic media. The calculation of the moveout is therefore performed by a 4th order NMO-correction with the rms-velocity and the effective eta value as variables. This approach is applied to data from a wideangle survey shot at Halvfarryggen, Dronning Maud Land, Antarctica. From this data we derived rms-velocities and effective eta values. These values were than recalculated to interval velocities and interval eta values to give a hint on the measure of anisotropy of the different layers. The results give first insight into the anisotropies at Halvfarryggen. |
format |
Conference Object |
author |
Diez, Anja Eisen, Olaf Hofstede, Coen Bohlen, Thomas Weikusat, Ilka Kipfstuhl, Sepp |
spellingShingle |
Diez, Anja Eisen, Olaf Hofstede, Coen Bohlen, Thomas Weikusat, Ilka Kipfstuhl, Sepp Determination of crystal orientation fabric from seismic wideangle data |
author_facet |
Diez, Anja Eisen, Olaf Hofstede, Coen Bohlen, Thomas Weikusat, Ilka Kipfstuhl, Sepp |
author_sort |
Diez, Anja |
title |
Determination of crystal orientation fabric from seismic wideangle data |
title_short |
Determination of crystal orientation fabric from seismic wideangle data |
title_full |
Determination of crystal orientation fabric from seismic wideangle data |
title_fullStr |
Determination of crystal orientation fabric from seismic wideangle data |
title_full_unstemmed |
Determination of crystal orientation fabric from seismic wideangle data |
title_sort |
determination of crystal orientation fabric from seismic wideangle data |
publisher |
Geophysical Research Abstracts Vol. 14, EGU2012-760, 2012 EGU General Assembly |
publishDate |
2012 |
url |
https://epic.awi.de/id/eprint/26032/ https://epic.awi.de/id/eprint/26032/1/EGU2012-760.pdf http://meetingorganizer.copernicus.org/EGU2012/EGU2012-760.pdf https://hdl.handle.net/10013/epic.39271 https://hdl.handle.net/10013/epic.39271.d001 |
genre |
Antarc* Antarctica Dronning Maud Land ice core |
genre_facet |
Antarc* Antarctica Dronning Maud Land ice core |
op_source |
EPIC3EGU General Assembly, Vienna, 2012-04-22-2012-04-27Geophysical Research Abstracts Vol. 14, EGU2012-760, 2012 EGU General Assembly |
op_relation |
https://epic.awi.de/id/eprint/26032/1/EGU2012-760.pdf https://hdl.handle.net/10013/epic.39271.d001 Diez, A. , Eisen, O. orcid:0000-0002-6380-962X , Hofstede, C. orcid:0000-0002-6015-6918 , Bohlen, T. , Weikusat, I. orcid:0000-0002-3023-6036 and Kipfstuhl, S. (2012) Determination of crystal orientation fabric from seismic wideangle data , EGU General Assembly, Vienna, 22 April 2012 - 27 April 2012 . hdl:10013/epic.39271 |
_version_ |
1810488531221479424 |