Seismic Exploration of the Deep Continental Crust

Part of the series Pure and Applied Geophysics(PAGEOPH) pp 123-138

Recovering Shear-wave Anisotropy of the Lower Crust: The Influence of Systematic Errors on Travel-time Inversion

  • T. BohlenAffiliated withInstitute of Geosciences
  • , W. RabbelAffiliated withInstitute of Geosciences
  • , T. WeissAffiliated withInstitute for Geology and Dynamics of the Lithosphere
  • , S. SiegesmundAffiliated withInstitute for Geology and Dynamics of the Lithosphere
  • , M. PohlAffiliated withGeophysical Institute

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Studies of seismic anisotropy in situ can help to discriminate between different rock types for the lower crust. In this context we investigate the sensitivity of an iterative linearized 3-D travel-time inversion scheme for transversely isotropic media with respect to two types of systematic errors: wrong velocities and interface topography of the hanging wall of the lower crust. The computations simulate realistic field conditions such as found for the Variscan crust at the Urach geothermal anomaly. The study focusses on the possible information content of split S M S arrivals observed along two orthogonal expanding spread profiles. It ensues that an imperfect knowledge of the layer geometry is of minor importance compared to errors in the velocities of the hanging wall. In particular, upper crust anisotropy has to be considered carefully. Generally, the anisotropy of transversely polarized shear waves (SH waves) was recovered with higher accuracy than the anisotropy of vertically polarized shear waves (SV waves).

Key words

Travel-time inversion seismic anisotropy lower crust shear waves Urach