On the pressure dependence of elastic parameters in porous and fractured rocks of the upper continental crust

在ICDP计划“大陆断裂系统中的能量和流体输运”中，该项目致力于大陆上地壳各向异性弹性参数的应力和流体压力依赖性。我们的项目遵循两个方面：（a）扩展的压敏性方法对各向异性介质的裂缝，包括非线性弹性的影响和（B）它的应用，从KTB岩心样品的实验室数据。这种方法建立了一组方程，允许解释速度与压力数据的压缩性和孔隙度的多孔和裂隙流体饱和岩石。这是一个非常少的理论方法，允许直接解释的应力依赖性地震速度的岩石物理参数。此外，它还引入了额外的和在一定程度上新的岩石特性，如压敏性和刚性和顺应性孔隙度。KTB深部实验室的136个岩心样品在高达350 MPa和更高的压差范围内测量了各向异性弹性速度和体积变形。这些数据将被分析和重新解释的各向异性压电灵敏度的方法。这将使我们更深入地了解KTB岩石在原位张应力状态下的应力相关弹性各向异性。这可能有助于解释观测到的和预测可能的各向异性的变化，由于孔隙流体压力的变化，在岩石中的上陆壳。

Within the ICDP-Program "Energy and Fluid Transport in Continental Fracture Systems" this project is dedicated to the stress and fluid pressure dependency of anisotropic elastic parameters in the continental upper crust. Our project follows two aspects: a) the extension of the piezosensitivity approach towards fractured anisotropic media including effects of nonlinear elasticity and (b) its application to laboratory data from KTB core samples. This approach establishes a set of equations which allow to interpret velocity vs. pressure data in terms of compressibility and porosity of porous and fractured fluid saturated rocks. It is one of the very few theoretical approaches allowing a direct interpretation of the stress dependency of seismic velocities in terms of rock physical parameters. Furthermore, it introduces additional and to some extend new rock characteristics, like the piezosensitivity and stiff and compliant porosity. Measurements of anisotropic elastic velocities and bulk deformation over a differential pressure range up to 350 MPa and higher are available for a set of 136 core samples from the KTB deep laboratory. These data will be analyzed and reinterpreted in terms of the anisotropic piezosensitivity approach. This will give a closer insight into the stress dependent elastic anisotropy of the KTB rocks under the in situ tensorial state of stress. It might help to explain observed and to predict possible anisotropy changes due to changes of pore fluid pressure in the rocks of the upper continental crust.