A NOVEL TOOL TO ESTIMATE RECENT TECTONIC DISPLACEMENT ALONG A LARGE STRIKE-SLIP FAULT: MAPPING OF OFFSET DRUMLINS AND LAKEFRONTS WITHIN THE CENTRAL CANADIAN CORDILLERA ON HIGH-RESOLUTION SATELLITE IMAGERY

The Northern Rocky Mountain Trench (NRMT) is a NNW-striking, dextral strike-slip fault system in western Canada, extending about 800 km from east of Prince George (53° 55' N; 122° 45' W) to Upper Liard (60° 3' N; 128° 54' W). In order to trace active fault branches along the NRMT precisely and to understand their late Quaternary short-term slip history, we conducted a tectonogeomorphic analysis, based on the evaluation of WorldView II^® satellite imagery with a resolution of 50 cm. Using these remote sensing techniques, we investigated several hundred disrupted geomorphic features such as lakefronts and drumlins, extending perpendicular across the NRMT fault system. The analysis of those Wisconsinan (late Pleistocene) structures enabled us to identify seven fault branches that show possible signs of fault activity over the last 10 ± 3 ka. Right-lateral offset measurements across the seven fault branches range from 7.5 to 45 m, which implies slip-rates of 1 to 6 mm/a during this period. This is consistent with the average slip-rate of about 2 mm/a since the Eocene. Assuming that the maximum single displacement of 20 m, observed at a lakefront, has accumulated during one single tectonic event, there is the possibility that this fault is capable of producing MW 7.7 earthquakes. Taking into account maximum single earthquake displacements of about 10 m across other major strike-slip fault systems around the globe, it seems more realistic that the maximum displacement of 20 m has accumulated during at least two tectonic events. This indicates the possibility of significant MW 7.4 earthquakes. Our study shows that the investigation of geomorphic structures using remote sensing techniques is a powerful method in order to investigate seismic hazard along major continental fault systems, where the geologic record and realtime measurements like GPS and seismicity can not provide reliable information about current fault activity.