The possible role of topographic and basin-edge effects in triggering the Mulgrave & Derry landslide during the 2010 Val-des-Bois earthquake, Québec (Canada)

Didier Perret, André Pugin, Rémi Mompin, Denis Demers

In the proceedings of: GeoOttawa 2017: 70th Canadian Geotechnical Conference; 12th joint with IAH-CNC

Session: Seismiscity and Sensitive Clay

ABSTRACT: In June 2010, an earthquake of moment magnitude M5.0 occurred in the Western Quebec seismic zone at about 60 km north-east of Ottawa, Canada. This moderate earthquake triggered a landslide in moderately sensitive clay deposits 18 km from the epicenter. Slope stability analyses conducted for static and drained conditions, as well as for undrained conditions, indicate an important pre-earthquake reserve of stability, which implies that some aggravating factors played a major role in triggering the landslide. In this paper, we investigate the possible role of topographic and basin-edge effects in triggering this landslide by modeling the two-dimensional seismic response of the slope and of the small sedimentary basin underlying the area. Basin-edge effects in particular, combined with a very high impedance contrast between the bedrock and the overlying soils, may have likely contributed to increase the amplitude and duration of the ground motion in a frequency range critical for slope stability.

RÉSUMÉ: Un séisme de magnitude du moment de 5.0 est du Québec à environ 60 km au nord-terrain dans des argiles moyennement sensibles. Des analyses de stabilité effectuées pour des conditions statiques et drainées, ainsi que pour des conditions non-drainées, indiquent une réserve de stabilité importante, ce qui implique que des facteurs aggravants ont dû jouer un rôle majeur dans le déclenchement de ce glissement. Nous investiguons dans cet article le rôle possible des effets topographiques et de bords de bassin dans le déclenchement du glissement de terrain à caractérisant le secteur. Les effets de bords de bassin en particulier, combinés à ule substratum rocheux et les sols au-mouvement du sol dans une gamme de fréquences critique pour la stabilité de la pente.

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