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| Titel |
Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model |
| VerfasserIn |
J. M. Carcione, F. Poletto, B. Farina, A. Craglietto |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 5, no. 2 ; Nr. 5, no. 2 (2014-09-25), S.1001-1010 |
| Datensatznummer |
250115341
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| Publikation (Nr.) |
 copernicus.org/se-5-1001-2014.pdf |
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| Zusammenfassung |
| The earth's crust presents two dissimilar rheological behaviors depending on
the in situ stress-temperature conditions. The upper, cooler part is
brittle, while deeper zones are ductile. Seismic waves may reveal the presence of the
transition but a proper characterization is required. We first obtain a
stress–strain relation, including the effects of shear seismic attenuation and
ductility due to shear deformations and plastic flow. The anelastic behavior
is based on the Burgers mechanical model to describe the effects of seismic
attenuation and steady-state creep flow. The shear Lamé constant of the
brittle and ductile media depends on the in situ stress and temperature
through the shear viscosity, which is obtained by the Arrhenius equation and
the octahedral stress criterion. The P and S wave velocities decrease as
depth and temperature increase due to the geothermal gradient, an effect
which is more pronounced for shear waves. We then obtain the P−S and SH
equations of motion recast in the velocity-stress formulation, including
memory variables to avoid the computation of time convolutions. The equations
correspond to isotropic anelastic and inhomogeneous media and are solved by a
direct grid method based on the Runge–Kutta time stepping technique and the
Fourier pseudospectral method. The algorithm is tested with success against
known analytical solutions for different shear viscosities. A realistic
example illustrates the computation of surface and reverse-VSP synthetic
seismograms in the presence of an abrupt brittle–ductile transition. |
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