Viscoelastic responses of a hard transition zone - Effects on postglacial uplifts and rotational signatures
A five-layer viscoelastic spherical model is used to calculate the transient displacements of postglacial rebound, the induced polar motions, and the temporal variations of the geopotential up to degree 8 of the zonal coefficients. Two models - one with two viscoelastic layers separated at 670 km, a...
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1991
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ftnasantrs:oai:casi.ntrs.nasa.gov:19910069302 2023-05-15T16:41:00+02:00 Viscoelastic responses of a hard transition zone - Effects on postglacial uplifts and rotational signatures Spada, Giorgio Sabadini, Roberto Yuen, David A. Unclassified, Unlimited, Publicly available Aug 1, 1991 http://ntrs.nasa.gov/search.jsp?R=19910069302 unknown http://ntrs.nasa.gov/search.jsp?R=19910069302 Accession ID: 91A53925 Copyright Other Sources 46 Earth and Planetary Science Letters; 105; 4, Au; 453-462 1991 ftnasantrs 2012-02-15T19:07:17Z A five-layer viscoelastic spherical model is used to calculate the transient displacements of postglacial rebound, the induced polar motions, and the temporal variations of the geopotential up to degree 8 of the zonal coefficients. Two models - one with two viscoelastic layers separated at 670 km, and the other with three layers in which a hard garnet layer lies between the upper and lower mantle - are compared. Forward modeling shows that it may be possible to discern the presence of a hard garnet layer with a viscosity of at least ten times greater than the upper mantle, on the basis of uplift data near the center of the former Laurentide ice-sheet and from polar wander and j2 data. Temporal variations of higher gravity harmonics, such as j6 and j8, can potentially place even tighter constraints on the rheological properties of the hard transition zone. A lower mantle viscosity between 2 and 4 x 10 to the 22nd Pa is generally preferred in models with a garnet layer which may be as large as 50 times more viscous than the upper mantle. Other/Unknown Material Ice Sheet NASA Technical Reports Server (NTRS) |
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46 Spada, Giorgio Sabadini, Roberto Yuen, David A. Viscoelastic responses of a hard transition zone - Effects on postglacial uplifts and rotational signatures |
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46 |
description |
A five-layer viscoelastic spherical model is used to calculate the transient displacements of postglacial rebound, the induced polar motions, and the temporal variations of the geopotential up to degree 8 of the zonal coefficients. Two models - one with two viscoelastic layers separated at 670 km, and the other with three layers in which a hard garnet layer lies between the upper and lower mantle - are compared. Forward modeling shows that it may be possible to discern the presence of a hard garnet layer with a viscosity of at least ten times greater than the upper mantle, on the basis of uplift data near the center of the former Laurentide ice-sheet and from polar wander and j2 data. Temporal variations of higher gravity harmonics, such as j6 and j8, can potentially place even tighter constraints on the rheological properties of the hard transition zone. A lower mantle viscosity between 2 and 4 x 10 to the 22nd Pa is generally preferred in models with a garnet layer which may be as large as 50 times more viscous than the upper mantle. |
format |
Other/Unknown Material |
author |
Spada, Giorgio Sabadini, Roberto Yuen, David A. |
author_facet |
Spada, Giorgio Sabadini, Roberto Yuen, David A. |
author_sort |
Spada, Giorgio |
title |
Viscoelastic responses of a hard transition zone - Effects on postglacial uplifts and rotational signatures |
title_short |
Viscoelastic responses of a hard transition zone - Effects on postglacial uplifts and rotational signatures |
title_full |
Viscoelastic responses of a hard transition zone - Effects on postglacial uplifts and rotational signatures |
title_fullStr |
Viscoelastic responses of a hard transition zone - Effects on postglacial uplifts and rotational signatures |
title_full_unstemmed |
Viscoelastic responses of a hard transition zone - Effects on postglacial uplifts and rotational signatures |
title_sort |
viscoelastic responses of a hard transition zone - effects on postglacial uplifts and rotational signatures |
publishDate |
1991 |
url |
http://ntrs.nasa.gov/search.jsp?R=19910069302 |
op_coverage |
Unclassified, Unlimited, Publicly available |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_source |
Other Sources |
op_relation |
http://ntrs.nasa.gov/search.jsp?R=19910069302 Accession ID: 91A53925 |
op_rights |
Copyright |
_version_ |
1766031440873521152 |