Base de données de recherche des TNO

Régions: Dehcho Region

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

Objectif(s): To improve the detection and characterization of earthquakes occurring within the northern Canadian Cordillera and to study the deep Earth structures to understand the formation and evolution of the Cordillera.

Description du projet: The objectives of this research project are 1) to improve the detection and characterization of earthquakes occurring within the northern Canadian Cordillera (comprising the Mackenzie and Richardson Mountains) and surrounding areas, which is one the most seismically active areas of Canada; and 2) to study the deep Earth structures to understand the formation and evolution of the Cordillera. To this end, 7 new seismograph stations will be installed across the Yukon and southwestern Northwest Territories. Each station will continuously record ground shaking and this data will be 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 new stations are located in the communities of Watson Lake, Faro, Keno City MacMillan Pass, Tungsten, Fort Liard, and Wrigley. The exact site locations will be selected in full consultation with the leadership of the affected communities. The installation requires about 5 to 10 person-days to carry out, with typically 2-3 persons working on a given site during 2 to 3 days. The network is also expanded with the 2 stations previously installed in Norman Wells and Colville Lake. 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: 1) The sensor is a 20 by 60 cm cylinder that measures very subtle ground motion due to earthquakes and other processes (strong winds, vehicles, etc.). The sensor is buried in the ground at a depth of about 2-5 m, whether in soil or bedrock. The 30 cm hole is either cored in bedrock using a coring drill or in soil using an auger. 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. 2) 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. This device is located within a thermally insulated box that also contains the power system, or attached to the communication system. 3) 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 a2m diameter dish. 4) The station is powered either by rechargeable batteries and 2-3 solar panels (“DC” station), or using an electrical outlet (“AC” station). 2 stations will have DC systems (MacMillan Pass and Tungsten), and the remaining 5 will 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. Site selection for the AC stations will be contingent upon access to a nearby electrical outlet within a community. 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. Fieldwork will occur in two phases: phase one (reconnaissance phase) will consist of site selection in full consultation with the concerned northern communities. Phase two (installation phase). Total fieldwork time for installation is estimated at 30-50 days. No field camp will be necessary. 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 will require 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. This research project has remarkable potential for communicating science to communities in the Yukon and Northwest Territories. Once the stations are installed, data flows in real-time to a central data archive and is accessible via internet. Therefore, each time an earthquake occurs, the data can be downloaded immediately and a report can be sent automatically to the concerned communities. The same tools can be used in schools for demonstrations about the Earth and the earthquake hazards. During the installation phase, visits to local schools and community centers can be 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. 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 Geoscience 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 June 1, 2015 to August 31, 2015.