Traveltime inversion and error analysis for layered anisotropy |
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| Authors: | Fan Jiang Hua-wei Zhou |
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| Institution: | 1. Laboratoire Jean Kuntzmann, Univ. Grenoble Alpes and CNRS, Grenoble, France;2. Univ. Bordeaux IMB, INRIA Bordeaux Sud-Ouest Team MEMPHIS, CNRS UMR 5251, France;1. Yangtze Center of Mathematics, Department of Mathematics, Sichuan University, Chengdu, 610064, China;2. Department of Mathematics, Sichuan University, Chengdu, 610064, China;1. Université d’Aix-Marseille, LMA UPR 7051 CNRS, 13625 Aix-en-Provence, France;2. DEN/DTN/STCP/LIET, CEA Cadarache, 13108 Saint Paul Lez Durance, France;3. LMA, CNRS UPR 7051, Université d’Aix-Marseille, Centrale Marseille, 13453 Marseille cedex 13, France;1. Department of Mathematics and ICES, The University of Texas at Austin, 1 University Station C1200, Austin, TX 78712, USA;2. Royal Institute of Technology KTH, 100 44 Stockholm, Sweden |
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| Abstract: | While tilted transverse isotropy (TTI) is a good approximation of the velocity structure for many dipping and fractured strata, it is still challenging to estimate anisotropic depth models even when the tilted angle is known. With the assumption of weak anisotropy, we present a TTI traveltime inversion approach for models consisting of several thickness-varying layers where the anisotropic parameters are constant for each layer. For each model layer the inversion variables consist of the anisotropic parameters ε and δ, the tilted angle φ of its symmetry axis, layer velocity along the symmetry axis, and thickness variation of the layer. Using this method and synthetic data, we evaluate the effects of errors in some of the model parameters on the inverted values of the other parameters in crosswell and Vertical Seismic Profile (VSP) acquisition geometry. The analyses show that the errors in the layer symmetry axes sensitively affect the inverted values of other parameters, especially δ. However, the impact of errors in δ on the inversion of other parameters is much less than the impact on δ from the errors in other parameters. Hence, a practical strategy is first to invert for the most error-tolerant parameter layer velocity, then progressively invert for ε in crosswell geometry or δ in VSP geometry. |
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