Surface-Wave Tomography of Western Canada Using a Two-station Approach
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Date
2017
Authors
Zaporozan, Taras
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Abstract
Seismic data from 106 station pair-paths, from the CNSN (Canadian National Seismic Network) and POLARIS (Portable Observatories for Lithospheric Analysis and Research Investigating Seismicity) seismic networks, were used to measure surface waves from earthquake events. Fundamental-mode Rayleigh-wave dispersion curves were generated and inverted to obtain dispersion maps and S-velocity cross-sections.
Results show a clear distinction between the Cordilleran and cratonic lithospheres. The Cordilleran lithopshere shows a low-velocity perturbation with values ranging from -2% to -5%, while the cratonic lithosphere shows a high-velocity perturbation with values ranging from 3% to 9%. The large range in perturbation between the Cordilleran and cratonic lithospheres resolves the Cordilleran/craton boundary, showing that the boundary is present down to 200 km in depth and dips under the cratonic lithosphere. A high-velocity anomaly within the already high velocity cratonic lithosphere is present under Great Slave Lake and is interpreted as preserved Precambrian slab material. Many small high-velocity perturbations, reaching about 4%, are present at depths of 300+ km throughout the survey, and interpreted as being remnants of the Kula or Farallon plates.
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Keywords
Tomography, Cordillera, Geophysics, Cordilleran Deformation Front, Two-station, Seismology, Craton