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TitleLandslide response to the 27 October 2012 earthquake (Mw 7.8), southern Haida Gwaii, British Columbia, Canada
AuthorBarth, S; Geertsema, M; Bevington, A R; Bird, A L; Clague, J J; Millard, T; Bobrowsky, P TORCID logo; Hasler, A; Liu, H
SourceLandslides 2019 p. 1-10, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20190352
Mediapaper; on-line; digital
File formatpdf; html
ProvinceBritish Columbia
NTS102O; 103B; 103C; 103F; 103G; 103J/01; 103J/02; 103J/03; 103J/04; 103K/01; 103K/02; 103K/03
AreaHaida Gwaii; Pacific Ocean
Lat/Long WENS-133.5000 -130.0000 54.2500 51.7500
Subjectssurficial geology/geomorphology; geophysics; Science and Technology; Nature and Environment; landslides; slope failures; debris flows; seismology; earthquakes; earthquake risk; earthquake damage; epicentres; earthquake mechanisms; tectonic history; depositional history; remote sensing; satellite imagery; photogrammetric surveys; airphoto interpretation; meteorology; Queen Charlotte Fault; 27 October 2012 Mw 7.8 earthquake; Land cover
Illustrationslocation maps; geoscientific sketch maps; photographs; satellite images; tables; histograms; rose diagrams; 3-D images; time series
ProgramCanadian Hazard Information Service
Released2019 11 09
AbstractIn this paper, we examine the influence of the 27 October 2012, Mw 7.8 earthquake on landslide occurrence in the southern half of Haida Gwaii (formerly Queen Charlotte Islands), British Columbia, Canada. Our 1350 km2 study area is undisturbed, primarily forested terrain that has not experienced road building or timber harvesting. Our inventory of landslide polygons is based on optical airborne and spaceborne images acquired between 2007 and 2018, from which we extracted and mapped 446 individual landslides (an average of 33 landslides per 100 km2). The landslide rate in years without major earthquakes averages 19.4 per year, or 1.4/100 km2/year, and the annual average area covered by non-seismically triggered landslides is 35 ha/year. The number of landslides identified in imagery closely following the 2012 earthquake, and probably triggered by it, is 244 or an average of about 18 landslides per 100 km2. These landslides cover a total area of 461 ha. In the following years - 2013-2016 and 2016-2018 - the number of landslides fell, respectively, to 26 and 13.5 landslides per year. In non-earthquake years, most landslides happen on south-facing slopes, facing the prevailing winds. In contrast, during or immediately after the earthquake, up to 32% of the landslides occurred on north and northwest-facing slopes. Although we could not find imagery from the day after the earthquake, overview reconnaissance flights 10 and 16 days later showed that most of the landslides were recent, suggesting they were co-seismic.
Summary(Plain Language Summary, not published)
A large number of landslides were identified in satellite and other imagery following the magnitude 7.8 earthquake off Haida Gwaii. This paper draws a link between the events, with strong evidence to suggest the landslides were co-seismic.

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