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Modélisation de la propagation des ondes élastiques générées par un séisme proche ou éloigné à l'intérieur d'une ville

Abstract : We can neither predict, nor fight against an earthquake. At the most, we can try to limit the damage and human losses provoked by an earthquake in a urban site. These sites, for practical reasons, are often built on sedimentary or lake basins. Nevertheless, the latter are the most dangerous sites in the event of an earthquake, because of the mechanical properties of the soil (Mexico-City in 1985, Izmit in 1999...).
A first step in attempting to limit the effects of earthquake in urban zones is to understand the mechanisms and phenomena involved in such an event. These are mainly of two strongly-coupled types: on the one hand, the mechanisms and phenomena related to the history of the incoming wave, and on the other hand, those related to the interaction of the incoming wave with the buildings.
We first show, numerically and theorically, that the solicitation of a configuration by a normally-incident plane wave does not correctly account for either the cause or the effects (response) when the source is relatively distant form the city, in a lateral sense. In this case, we show that the characteristics of the coda, noticed inside the city, are partially included in the incoming wave this being due to mode excitation of the configuration in the basence of the buildings.
We then exhibits the principal mechanism of the interaction of this wave with the buildings. The presence of the latter induces a strong modification of the displacement field inside the city leading to an effect that is more devastating (mainly in the shear-horizonatl case) than in the absence of buildings. This enhancement is essentially due to a modification of the mode of the total (i.e. building + soil) configuration.
This study constitutes an analytical proof of the importance and the complementarity of these two mechanism classes for understanding the phenomena involved in earthquakes at urban sites.
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https://tel.archives-ouvertes.fr/tel-00115636
Contributor : Jean-Philippe Groby <>
Submitted on : Wednesday, November 22, 2006 - 1:55:34 PM
Last modification on : Thursday, January 23, 2020 - 6:22:03 PM
Long-term archiving on: : Tuesday, April 6, 2010 - 6:58:04 PM

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  • HAL Id : tel-00115636, version 1

Citation

Jean-Philippe Groby. Modélisation de la propagation des ondes élastiques générées par un séisme proche ou éloigné à l'intérieur d'une ville. Physique mathématique [math-ph]. Université de la Méditerranée - Aix-Marseille II, 2005. Français. ⟨tel-00115636⟩

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