HR: 0830h
AN: T51F-0227    [PDF]
TI: A Single Method for the Inversion of Anisotropic Data Sets With Application to Structural Studies
AU: David, C
EM: christian.david@geol.u-cergy.fr
AF: UMR CNRS 7072 Univ. Cergy-Pontoise, Av. du Parc - Le Campus - Bat. I, Cergy-Pontoise, 95031 France
AU: * Louis, L
EM: laurent.louis@geol.u-cergy.fr
AF: UMR CNRS 7072 Univ. Cergy-Pontoise, Av. du Parc - Le Campus - Bat. I, Cergy-Pontoise, 95031 France
AU: Robion, P
EM: philippe.robion@geol.u-cergy.fr
AF: UMR CNRS 7072 Univ. Cergy-Pontoise, Av. du Parc - Le Campus - Bat. I, Cergy-Pontoise, 95031 France
AB: Due to the intrinsic characteristics as to the shape and arrangment of their components, rocks are naturally anisotropic, that is traditionally pointed out through the measurement in different directions of a given physical property. These anisotropies are in general easy to observe and quantify but not to interprete in terms of microstructure or, what remains the same, in terms of deformation if the measurements are performed for a structural study. For instance, a usual problem is to distinguish, giving an anisotropy fabric, the deformation contribution from the inherited part. Here, a unified method to analyse magnetic susceptibility and P-wave velocity data is proposed, assuming that both measurement sets can be described by a second rank tensor, which is rigorously true only for the magnetic data. For the velocity data, this hypothesis is discussed by estimating the error made during inversion with respect to theoretical estimations for transverse isotropic media. We find that the error mostly falls below 1% for simulations on published experimental data for several sandstones and limestones. Therefore our analysis promotes the use of a unique and simple method to analyse anisotropy from different data sets in structural applications. We also discuss the best strategy for data sampling in order to get a comprehensive knowledge of the anisotropic behaviour of rocks in structural studies. The method is applied to different sedimentary rocks (mainly sandstones), retrieved in both deformed and undeformed structures. We emphasize that combining data sets for different physical properties and using a single inversion scheme leads to a better understanding of the deformation processes at the microstructural scale.
DE: 5102 Acoustic properties
DE: 5194 Instruments and techniques
SC: Tectonophysics [T]
MN: 2003 Fall Meeting