Estimativa de anisotropia local de dados de onda P em experimentos de VSP multiazimutal

Adriano C. R. Barreto, Raiza de N. A. Macambira, Ellen N. S. Gomes e Ivan Psencik


Inversion scheme for the local determination of anisotropy from P-wave data obtained during a multiazimuth multiple-source VSP experiment is studied. The inversion is based on an approximate formula relating linearly weakly anisotropic (WA) parameters describing the medium at a receiver and the vertical components of slowness vectors and complete polarization vectors measured at the same point. The optimum choices of the reference isotropic medium and of the unit normal of the wave in the reference medium are presented. Efficiency of the inversion scheme, stability and sensitivity of its results with respect to varying number of profiles, types of used waves (direct and/or reflected) and noise levels are analyzed. It is also shown that although only P-wave data are used, it is possible to estimate the orientation of the axis of symmetry of a TI medium from estimated parameters.

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In: Seismic Waves in Complex 3-D Structures, Report 21, pp. 63-68, Dep. Geophys., Charles Univ., Prague, 2011.