Base de données de recherche des TNO

Régions: Dehcho Region

étiquettes: physical sciences, geology, seismology, monitoring, remote sensing

Objectif(s): To continue the detection and characterization of earthquakes occurring within the northern Canadian Cordillera (Mackenzie Mountains) and surrounding areas; and to study the Earth structures at large depths (0 to 100 km).

Description du projet: The objectives of this research project are: 1) to continue the detection and characterization of earthquakes occurring within the northern Canadian Cordillera (Mackenzie Mountains) and surrounding areas, which are one the most seismically active areas of Canada; and 2) to study the Earth structures at large depths (0 to 100 km) to understand the formation and evolution of the Cordillera. To this end, 7 seismograph stations were installed throughout the Yukon and western Northwest Territories in 2013. Each station continuously records ground shaking and these data are processed to monitor earthquake activity and to study the Earth’s interior. The methodology employed in this research consists of installing one seismograph station at each of the selected sites (7 stations in total), broadly distributed in the Yukon and Northwest Territories. Stations are installed in proximity to communities and roads for easy access. More specifically, the stations are located in the communities of Watson Lake, Faro, Mayo, along the North Canol Road at Twin Creeks airport, along the Nahanni Range road at the Hyland airport, Fort Liard, and Wrigley. The exact site locations were selected in full consultation with the leadership of the affected communities. The stations were installed in the summer of 2013 and have been operating for 4 years. Each seismograph station is made up of 4 components: 1) the sensor; 2) the recording device; 3) the communication system and 4) the power system. Each component and its installation are detailed below: The sensor is a ~20 by 60 cm cylinder that measures very subtle ground shaking due to earthquakes and other processes (strong winds, vehicles, etc.). The sensor is buried (using shovel or auger) in the ground at a depth of about 2 m below the surface. The sensor is placed in the hole and the hole is filled with sand to thermally insulate the instrument. The sensor is linked with the recording device by a protected cable. The recording device is a small box with electronic components that receives the electronic signal from the sensor and converts it to a digital signal (seismograms). This device is located within a thermally insulated box that also contains the power system and the communication system. The communication system receives the signal from the recording device and sends it to a satellite relay using an antenna. The station communicates with the satellite using a 2-meter diameter dish. The station is powered either by rechargeable batteries and 4 solar panels (“DC” station), or using an electrical outlet (“AC” station). 2 stations have DC systems (Twin Creek and Hyland airports), and the remaining 5 have AC systems. DC-powered stations are located in remote areas along roads and outside communities. AC systems require the use of power from either a nearby generator or through the power grid. The footprint of one station is approximately 3 meters by 3 meters. Each station records ground shaking continuously and autonomously: no visit is required at the site once the station is installed. Occasional or yearly visits may be required to realign the dish or repair damaged equipment. During the operational phase, the stations will require minimal scheduled maintenance. To reduce the impacts, site visits are scheduled once per year unless occasional station repair is necessary. Each site visit requires one day of fieldwork per station, or about 10 days total per year. Once the project is terminated the stations are pulled out and the site is restored to its former undisturbed state. No equipment is left on site and no contaminant is used to install or remove the stations. The mountains of northwestern Canada (Mackenzie Mountains) generate numerous earthquakes that can be harmful to villages and their inhabitants. The same mountains are also host to many mineral deposits and geothermal energy of economic value. Investigating these hazards and resources is the purpose of this project, which leads to eventual economic benefits. The project also represents a great educational tool to learn about the formation of mountain chains and their fragility and earthquake hazard potential. During the installation phase, visits to local schools and community centers were organized to show what the stations will be used for and how the schools can take advantage of the data to teach about science. During the recording phase, earthquake reports can be automatically generated and sent to local communities and authorities for hazard concerns - which has not happened yet since the installation of the network. A webpage containing automatic reports and earthquake activity recorded using the seismic network will be created. Scientific papers and theses that use data from the network can be made publicly available on the website. In addition, research done using the data (either for the characterization of earthquakes or the research on Earth structures) will be presented at local geoscience forums (e.g., Yellowknife Geoscience Forum and Yukon Geosicence Forum and Trade Show) as well as national conferences (e.g., Canadian Geophysical Union Annual Meeting). The fieldwork for this study will be conducted from July 1, 2018 to August 25, 2018.