Rheology of the Lower Crust: Laboratory Data and Field Observations
21 giugno 2007 ore 10:00 | Prof. G. Dresen, Direttore della Sezione Deformation and Rheology・del GFZ di Potsdam | Sala Conferenze - Roma | Sede Centrale
Damage and crack porosity can result in a decrease of the mechanical strength of the rock, the development of elastic and mechanical anisotropy and the enhancement of transport properties.
First, using Non-Interactive Crack Effective Medium (NIC) theory as a fundamental tool, it is possible to calculate dry and wet elastic properties of cracked rocks in terms of a crack density tensor, average crack aspect ratio and mean crack fabric orientation using the solid grains and fluid elastic properties. Using the same tool, we show that the anisotropy, the shear wave splitting and the dispersion of elastic waves can be derived for anisotropic crack fabrics. The evolution of elastic properties in high porosity rocks is then considered. A new isotropic effective medium model (IEM) is now used, which considers the rock as a mixture of spheroidal pores and penny-shaped cracks. In particular the evolution of the Vp/Vs ratio can be derived and shows the important role played by the mechanical coupling of fluid with low aspect ratio cracks (< 10-2).
First, using Non-Interactive Crack Effective Medium (NIC) theory as a fundamental tool, it is possible to calculate dry and wet elastic properties of cracked rocks in terms of a crack density tensor, average crack aspect ratio and mean crack fabric orientation using the solid grains and fluid elastic properties. Using the same tool, we show that the anisotropy, the shear wave splitting and the dispersion of elastic waves can be derived for anisotropic crack fabrics. The evolution of elastic properties in high porosity rocks is then considered. A new isotropic effective medium model (IEM) is now used, which considers the rock as a mixture of spheroidal pores and penny-shaped cracks. In particular the evolution of the Vp/Vs ratio can be derived and shows the important role played by the mechanical coupling of fluid with low aspect ratio cracks (< 10-2).