Slave - Northern Cordillera Refraction Experiment (SNORE 97)

Regions: Dehcho Region, North Slave Region

Tags: physical sciences, geology, tectonic movement, historical data, lithology, geophysics, seismic line

Principal Investigator: Clowes, Ron M. (1)
Licence Number: 12909
Organization: University of British Columbia
Licensed Year(s): 1997
Issued: May 26, 1997
Project Team: Dr. R.M. Ellis, UBC, Vancouver; Dr. I. Asudeh, GSC, Ottawa; Dr. G.D. Spence, U. of Victoria, Victoria; plus a field crew (approx. 60 people)

Objective(s): SNORE 97: primary purpose to determine velocity structure of the crustal and sub-crustal lithospheric mantle of the differing geological domains crossed by the survey lines & relationship of the interpreted results to other geophysical and geological data. Will help define the current tectonic structure of these domains and an understanding of past history. Four survey lines planned, all using existing roadways. Line 11 is within the NWT & runs westward from Tibbit Lake to Nahanni Butte. The other 3 lines are located in northern BC & the Yukon. The NWT line has 12 sites selected based on gov't guidelines for distances which structures etc. must be away from the site for the planned size of the chemical explosive charge & the scientific needs of the experiment. Planned charge sizes range from 3000 kg of commercial explosive distributed among 3 holes to 400 kg of explosive in 1 hole. During the experiment 620 portable seismic recorders will be deployed at about 1 km intervals along the road allowances of highways 4, 3, 1 and 7. They are left in place 1-3 days. Fort Providence is the field headquarters location.

Project Description: This refraction seismic project is part of larger transect which extends from Yellowknife to Stewart on the west coast of BC. Part of the sequence of Earth & Ocean Science studies to provide an in-depth image of the deep structure of the Earth throughout the region and will help to define the sequence of emplacement of various types of rock formations in the region. Pre-experiment: 1) Flag recording sites & determine their precise location with GPS procedures. Each site, staked with line and station number for easy location. 2) Drilling holes & loading appropriate explosives at each seismic source site. Supply of explosives & loading holes done by recognized explosives manufacturer. Drilling involves drill rigs which drill 200 mm diameter holes to depths of 50-60 m. 1-3 holes (30 m apart) drilled at each site. Drill crew consists of 2 large vehicles, drill rig, & water truck & personnel vehicle. The hole is infilled with cuttings &/or water, & sealed at the surface to await detonation. Approx. 2-3 weeks to drill & load 12 sites. Will be done in July. In late August/early September, instruments would be prepared for deployment. The deploying crews go by road to assigned recording sites. At each site, small hole (50 cm deep & 20-30 cm diameter) dug to place the seismometer firmly in the ground; the hole is filled & tamped. If the site is on bedrock, seismometer will be placed on bedrock. The seismometer is connected to a recorder which records ground vibrations. Following detonations, crews are sent to pick of equipment & related materials. Data recorded by each seismograph is uploaded into a computer. Data analysis & interpretation will take 2-3 years to complete.