NWT RESEARCH DATABASE

Tags: geology, permafrost, sediment chemistry, seismology, Beaufort Sea, coastal environment

Objective(s): To provide information on tsunami hazard and possible enhanced ground shaking resulting from earthquakes.

Project Description: Industry and regulators require information on seismicity and its effect on engineering structures both at a regional and local scale. The primary source of this information is the National Building Code of Canada’s Seismic Hazard Value map. Ongoing work undertaken as part of the 2015 revision of this map suggests that an increased seismic (earthquake) hazard exists in the Mackenzie-Beaufort area. To provide information on tsunami hazard and possible enhanced ground shaking resulting from earthquakes, the research team propose a 3-year field study that will build on preliminary investigations conducted in summer 2014. Activity 1: For the summer of 2015 the research team propose to establish a small tent field camp in the North Head area of northern Richards Island. The research team will continue the stratigraphic examinations of coastal exposures for evidence of materials that could have been deposited by a tsunami. This field work will include the following tasks: 1. the description and sampling of coastal exposures in the North Head area of northern Richards Island; 2. using a small inflatable boat and a fish-finder sonar conduct simple bottom mapping of several lakes to determine their depth and morphology; 3. collection of shallow 2-3 m long sediment cores in drained lake basins where there are no coastal exposures to look for evidence of paleo-tsunamis. A dry auger and/or push-core will be used for this purpose taking a 1-3” diameter core sample. The research team will not use a drilling fluid and expect no contamination of surface sediments. Each core hole will be backfilled with cuttings after completion; and, 4. A small, 2 kg (5 lb), electric powered Unmanned Aerial Vehicle (UAV) will be used to collect low-altitude (<90 m) aerial imagery at North Head. The purpose of this survey is to map permafrost and coastal features at North Head in high resolution 3D. One or two, small-foot print (<7 sq km) surveys will be undertaken, each taking less than 4 hours to complete. These surveys will be conducted following Transport Canada’s Canadian Aviation Regulations (CARs), that ensure safe conditions exist at all times during the survey, including minimum distances from people and other potential hazards. The UAV operator will maintain visual contact with the UAV at all times during the surveys and a second “spotter” person will also be present. No disturbance to wildlife will take place (i.e. surveys will be not be commenced if wildlife are nearby and surveys will be terminated if wildlife are observed while the UAV is airborne). Activity 2: This second field season will add to the spatial coverage of the data collected at approximately 20 locations in a preliminary field activity undertaken in summer 2014. A portable, low-cost engineering geology instrument (Tromino) will be used to record ambient vibrations of the soil. Sites will primarily be at industry well locations with varying permafrost conditions where existing geological, geophysical, and geotechnical data exist that will aid in the site response analysis. Additional sites may be chosen on an opportunity basis in collaboration with other Natural Resources Canada researchers. Data collection is relatively straightforward: 1) A small section (30 cm x 30 cm) of the ground surface is prepared to ensure good contact with the instrument by removing any loose debris such as sticks or thick moss cover. 2) The instrument is placed on the ground surface with its four short (5 cm) metal prongs inserted into the soil. 3) The instrument is left to record for 30 minutes. Data will be recorded at a minimum of three locations at each site. It is expected that each site can be completed in 2 hours. A series of photos describing the instrument are provided as an attachment. The resultant seismic amplification information will be analysed and could be used to help constrain the geological and geotechnical models used in the computation of the Seismic Hazard Values in the 2020 National Building Code of Canada. This in turn will guide the design of new infrastructure that will be required for the development of resources in the Mackenzie-Beaufort area. A post-field report and copies of all scientific contributions (scientific papers, maps, and databases) will be provided to the communities in the Inuvialuit Settlement Region through the Aurora Research Institute. The fieldwork for this study will be conducted from July 28, 2015 to August 14, 2015.