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| Tectonics and Structural Geology |
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Information - TS3.2 Rupture and creep in the lower continental crust: Evidence from geophysical, geological and petrological observations
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Event Information |
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The conventional rheological model of the lithosphere assumes the existence of a weak
aseismic and viscously deforming lower crustal layer, sandwiched between an overlaying brittle crust and a strong upper mantle. This simple “jelly sandwich” model appears to be
consistent with many seismological observations (earthquakes confined to the upper crust),
by extrapolated laboratory experiments (creep of most rocks at T>300°-500°) and by a
laminated lower crust (believed to originate by creep processes). However, in several tectonic areas earthquakes and tremors are observed in the lower crust, some of them at temperatures
apparently above about 500°C. Presently, various explanations exist. Metamorphic processes linked to fluids from de-hydration processes or intrusions, special structures like shear zones,
lamellae or anisotropy may each play a role. Certainly, seismicity, structure and mechanical strength have to be analysed, and it has to be discussed whether the lower crust under certain conditions is possibly rheologically stronger than the uppermost mantle as suggested by some researchers.
It is the aim of this session to combine interdisciplinary knowledge from a large geoscience community in order to attack the problem of rupture and creep processes in the lower continental crust. It is considered to be one of the major problems of lithospheric research.
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