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| Titel |
The rheology of the oceanic and continental lithosphere |
| VerfasserIn |
Dan McKenzie  , James Jackson, Keith Priestley |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039332
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| Zusammenfassung |
| The rheology of the lithosphere controls the transmission of stress within
plates and the deformation that occurs at their boundaries. In oceanic
regions determination of earthquake depths and of the elastic thickness show
that the upper part of the lithosphere, where the temperature is less than
600oC, behaves as a brittle solid. At higher temperatures stresses are
relaxed over geological time scales by creep. This behaviour is that expected
from laboratory experiments on dry peridotites. In contrast there is as yet
no general agreement about the rheology of continental lithosphere, which has
been the subject of a long-running controversy. The depths of continental
intraplate earthquakes determined from P and S travel times are often as great
as 100 km, and the elastic thickness determined from gravity and topography is
commonly 100-150 km beneath shields. At such depths the temperature exceeds
1000oC, and in the laboratory stresses are relaxed at such temperatures within
hours. Detailed examination of the waveforms of continental earthquakes can
be used to determine their depths to an accuracy of about 5 km, and shows that
the depths determined from travel times alone are sometimes in error by as
much as 70 km. All depths so far determined from waveforms of continental
earthquakes whose magnitude exceeds 5.5 are within the crust, and none occur
where that estimated temperature exceeds 600oC. Determinations of the elastic
thickness using the coherence method are affected by erosion, postglacial
uplift and dynamic support, all of which cause the value estimated from the
observations to exceed the true value. When proper account is taken of these
effects estimates of the elastic thickness of continental lithosphere are
everywhere less than the depth od the 600oC isotherm and are also less than
the seismogenic thickness. |
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