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| Titel |
Gravity and Flexure Modelling of Subducting Plates |
| VerfasserIn |
J. A. Hunter, A. B. Watts, SO 215 Shipboard Scientific Party |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069742
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| Zusammenfassung |
| The long-term strength of the lithosphere is determined by its flexural rigidity, which is
commonly expressed through the effective elastic thickness, Te. Flexure studies have
revealed a dependence of Te on thermal age. In the oceans, loads formed on young (70 Ma) seafloor. In the continents, loads
on young (1000 Ma)
lithosphere. Recent studies have questioned the relationship of Te with age, especially at
subduction zones, where oceanic and continental lithosphere are flexed downwards by up
to ~6 km over horizontal distances of up to ~350 km. We have therefore used
free-air gravity anomaly and topography profile data, combined with forward and
inverse modelling techniques, to re-assess Te in these settings. Preliminary inverse
modelling results from the Tonga-Kermadec Trench – Outer Rise system, where the
Pacific plate is subducting beneath the Indo-Australian plate, show large spatial
variations in Te that are unrelated to age. In contrast to the southern end of the system,
where Te is determined by the depth to the 600Ë C and 900Ë C isotherms, the
northern end of the system shows a reduction in strength. Results also suggest a
reduction in Te trenchward of the outer rise that is coincident with a region of pervasive
extensional faulting visible in swath bathymetry data. In a continental setting, the Ganges
foreland basin has formed by flexure of the Indo-Australian plate in front of the
migrating loads of the Himalaya. Preliminary forward modelling results, using the
Himalaya as a known surface topographic load, suggest that Te is high – consistent
with the great age of Indian cratonic lithosphere. However, results from inverse
modelling that solves for unknown loads (vertical shear force and bending moment)
show significant scatter and display trade-offs between Te and these driving loads. |
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