Resumo

MALISCHEWSKY, Peter G.; FORBRIGER, Thomas  e  LOMNITZ, Cinna. Unusual, equivocal Rayleigh-dispersion curves for simple models taking into account the special propagation conditions in the valley of Mexico City (CDMX) - Preliminary results. Geofís. Intl [online]. 2017, vol.56, n.1, pp.7-12. ISSN 2954-436X.  https://doi.org/10.19155/geofint.2017.056.1.1.

Other than commonly assumed in seismology, the phase velocity of Rayleigh waves not necessarily is a single-valued function of frequency. We demonstrate this for the first higher mode in simple models of a homogeneous layer on top of a homogeneous halfspace (LOH), which are used for the subsurface of the Texcoco zone in Mexico City valley in previous studies. In the structure of a homegenous layer with fixed bottom (LFB) the phenomenon exists for values of Poisson’s ratio between 0.19 and 0.5 and is most pronounced for P-velocity being three times S-velocity (Poisson’s ratio of 0.4375). This type of dispersion is demonstrated and a discussion of their possible fatal consequences for methods customarily used in seismology for dispersion analysis and synthesis of dispersion relations is presented.

Palavras-chave : Rayleigh waves; dispersion; ambiguity; Mexico City valley.

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