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Guided Waves and Rayleigh Leaking Modes With Outpost Algorithm
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 77th EAGE Conference and Exhibition 2015, Jun 2015, Volume 2015, p.1 - 5
Abstract
Near surface P-wave structure can be estimated by inverting dispersion curves of the guided waves.
Guided waves are associated with special complex roots of dispersion equations. For a model of a solid waveguide overlying a solid half-space, collection of guided waves and Rayleigh leaking modes represent complete set of leaking modes comprising the total elastic wavefield. Dispersion curves inversion requires an efficient, automated and accurate algorithm to compute complex roots of dispersion equation. We propose an application of the so-called outpost method that searches for moments of leaking modes crossing some line in complex plane called an outpost. This approach allows to achieve any desired accuracy by individual continuation of leaking modes as curves parameterized by frequency starting from the outpost. We suggest a particular shape of the outpost line to take into consideration all possible leaking modes arising up to a certain chosen frequency of interest. We test the approach using a near surface model giving rise to strong guided and Rayleigh leaking waves and verify the accuracy of the algorithm by comparison with velocity-frequency spectra obtained by full waveform elastic modeling.