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| Titel |
Glacial Isostatic Adjustment with ICE-6G{\_}C (VM5a) and Laterally
Heterogeneous Mantle Viscosity |
| VerfasserIn |
Tanghua Li, Patrick Wu, Holger Steffen |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137720
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| Publikation (Nr.) |
 EGU/EGU2017-524.pdf |
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| Zusammenfassung |
| Recently, Peltier et al. (2015) introduced the ICE-6G_C (VM5a) ice-earth model pair, which
has successfully explained many observations of Glacial Isostatic Adjustment (GIA)
simultaneously. However, their earth model used (VM5a) to infer the ice history (ICE-6G_C)
is laterally homogeneous with viscosity profile varying in the radial direction only. Since
surface geology and seismic tomography clearly indicates that the Earth’s material properties
also vary in the lateral direction, laterally heterogeneity must be included in GIA models.
This can be achieved by using the Coupled-Laplace-Finite-Element method (Wu 2004) to
model GIA in a spherical, self-gravitating, compressible viscoelastic Earth with linear
rheology and lateral heterogeneity. In fact, Wu et al (2013) have used such model with GIA
observations (e.g. global relative sea level data, GRACE data with recent hydrology
contributions removed and GPS crustal uplift rates) to study the thermal contribution to
lateral heterogeneity in the mantle. Their lateral viscosity perturbations are inferred from
the seismic shear wave tomography model S20A (Ekstrom & Dziewonski 1998)
by applying a scaling law, which includes both the effect of anharmonicity and
anelasticity. The thermal contribution to seismic tomography, which is represented
by the beta factor in the scaling relationship, is searched in the upper and lower
mantle, for the best combination that gives the best fit between GIA predictions and
observations. However, their study is based on ICE-4G only, and the new ice-earth
model pair may give other best beta value combinations in the upper and lower
mantle.
Here, we follow the work of Wu et al (2013) but use the new ICE-6G_C ice model
instead. The higher resolution seismic tomography model by Bunge & Grand (2000)
substitutes S20A. Earth model VM5a is used as the reference background viscosity model.
The full viscosity model is obtained by superposing the background model with the lateral
viscosity perturbations inferred from the seismic tomography model (Bunge & Grand 2000)
logarithmically. The preliminary results of these and other background viscosity profiles will
be presented.
References:
Bunge, H.-P. & Grand, S. P. (2000). Mesozoic plate-motion history below the
northeast Pacific Ocean from seismic images of the subducted Farallon slab. Nature,
405(6784):337-340.
Peltier, W., Argus, D., and Drummond, R. (2015). Space geodesy constrains ice age
terminal deglaciation: The global ICE-6G_C (VM5a) model. Journal of Geophysical
Research: Solid Earth, 120(1): 450-487.
Wu, P. (2004). Using commercial finite element packages for the study of earth
deformations, sea levels and the state of stress. Geophysical Journal International, 158(2):
401-408.
Wu, P., Wang, H.S. & Steffen, H. (2012). The role of thermal effect on mantle seismic
anomalies under Laurentia and Fennoscandia from observations of Glacial Isostatic
Adjustment. Geophysical Journal International, 192(1):7-17. |
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