Caveats in Multi-modal Inversion of Seismic Surface Wavefields |
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| Authors: | A L Levshin G F Panza |
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| Institution: | (1) Center for Imaging the Earths Interior, Department of Physics, University of Colorado at Boulder, Boulder, CO, 80309-0390, U.S.A;(2) Department of Earth Sciences, University of Trieste and the Abdus Salam International Center for Theoretical Physics - SAND group, Trieste, Italy |
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| Abstract: | We consider several examples demonstrating that the formal modal representation of surface wavefields often does not describe
adequately observable wave parameters, such as the phase and group velocity dispersion of higher modes. The main reason for
this is the existence in the medium of several waveguides or weakly coupled wavefields in the same waveguide. In such cases
the separation of neighboring higher modes may be impossible, and observed dispersion curves may significantly differ from
the ones predicted by the theory. From the example related to the studies of the crustal and upper mantle structure we found
that the difficulty in the separation of first and second crustal higher modes can be overcome by applying a special inversion
procedure. This procedure ignores the existence of a low velocity layer in the upper mantle when fitting the observable higher-mode
dispersion curve to the one predicted by the model. |
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| Keywords: | Surface waves waveguides phase and group velocity inversion |
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