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Instituto de Investigação
em Vulcanologia e Avaliação de Riscos
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Painéis ► em encontros internacionais


Referência Bibliográfica

TEVES-COSTA, P., VICÊNCIO, H., BORGES, A., WALLENSTEIN, N., GASPAR, J.L., SENOS, M.L. (2002) - Are microtremor data useful for site effects estimation? - Some results. ESC - XXVIII General Assembly. Génova, Itália, 1 - 6 de Setembro (Poster).


Microtremor surveys are widely used for microzonation purposes and, in particular, for site effects estimations. The definition of “site effect” requires that the same effect must be observed in a certain site, independently of the seismic excitation. This can be checked by the analysis of different seismic events recorded in the site. Classically, the standard spectra ratio – SSR (ratio between the spectra of the seismic event recorded in the site and the spectra of the same seismic event recorded in a reference site located on rock) is used for this purpose. More recently H/V ratio determined from seismic records performed at the site, have been used to check the existence of site effects. Besides, the H/V ratio determined from microtremor records has also been widely used for the same purpose.
In order to compare these different approaches, we analysed earthquake records and microtremor records from some selected sites, which present different geological conditions. H/V ratios, obtained from earthquake records and microtremor records, were determined and, whenever possible, SSR were also determined. The comparison of the obtained spectral ratios showed that the agreement between the three approaches is dependent on the site geological conditions. This work was partially performed in the aim of the SESAME project (EVG1-CT-2000-00026) in which this problem is being investigated for a large number of sites, located in different countries and exhibiting a large variety of geological conditions.