Search

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The concept of earth quake vulnerability is used in this work to predict the average damage that buildings are likely to experience on a large scale with the occurrence of an earthquake of given intensity. The use of the vulnerability concept is considered in the context of the particular typology of reinforced concrete buildings, which are commonly encountered in northern Morocco and which have not been engineered with adequate earthquake protection. The vulnerability scale is adapted based on the Italian method called “Gruppo Nazionale per la Difesa dai Terremoti” (GNDT) by adjusting the weighting coefficients to better match the local architectural characteristics of these types of buildings. A correlation is then proposed between the damage index considered as the main tracked effect and the causes that are herein idealized through the vulnerability concept. The results of field observations performed after the strong earthquake in Al Hoceima of magnitude 6.3 that hit the region of northern Morocco in 2004 have shown that the proposed method can correctly evaluate vulnerability. Relative fragility curves for this building typology are finally depicted. Dans ce travail, le concept de vulnérabilité sismique est utilisé afin de prédire le niveau moyen des dégâts pouvant se produire à grande échelle dans les bâtiments sous l’action d’une secousse sismique d’intensité connue. L’emploi de la notion de vulnérabilité est considéré dans le contexte de la typologie particulière des constructions en béton armé communément rencontrées au Nord du Maroc et n’ayant pas fait l’objet d’une conception parasismique assurant une protection adéquate. L’échelle de vulnérabilité est adaptée à partir de la méthode italienne dite « Gruppo Nazionale per la Difesa dai Terremoti » (GNDT), où un recalage des coefficients de pondération est effectué afin de mieux coller aux caractéristiques architecturales locales de ce type de constructions. Une corrélation est ensuite proposée entre l’indice des dégâts considéré comme l’effet principal recherché et les causes schématisées formellement à travers la notion de vulnérabilité. Les résultats d’une enquête menée sur le terrain après le fort tremblement de terre de magnitude 6,3 qui a frappé la région d’Al Hoceima au Nord du Maroc en 2004 ont montré que la méthode proposée permet d’évaluer correctement la vulnérabilité. Les courbes de fragilité relatives à cette typologie de bâtiments ont été enfin dressées. [ABSTRACT FROM AUTHOR]

Abstract: This study is based on an analysis of seismic, gravimetric and magnetic data to model the structure of the Dover Straits area. The Dover Straits are set in a transitional position within the Brabant para-autochthon, which lies between the Ardennes allochthon to the south and the Brabant Massif to the north. The seismic profiles show that this area is characterised by several superimposed Mesozoic basins, whose evolution has been controlled by the reactivation of Lower Palaeozoic faults. In common with the adjacent Weald–Wessex and southern North Sea basins, the Dover Straits area records a Jurassic extensional phase and a post-Cretaceous tectonic inversion. The geophysical modelling reveals the presence of a basement to these Mesozoic basins that exhibits Ordovician to Silurian structures, which cannot be detected on the seismic reflection profiles. In contrast to earlier interpretations, the modelling presented here suggests that the Brabant Massif continues southward beyond the Dover Straits and under the Brabant para-autochthon. Gravity data also provides evidence for the presence of granitic body at depth, in the vicinity of Km 27 on the seismic profile, which may have driven the uplift of the Silurian rocks in the area of the Straits. Similar granitic intrusions have been proposed to explain gravity anomalies along the Rhenohercynian Margin in Belgium, eastern and southern England. The geophysical modelling demonstrates the continuity of the basement and Mesozoic basin structures across the Dover Straits, suggesting a common geological evolution of the adjacent southern England–northern France regions. To cite this article: B. Minguely et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]