Lithospheric structure and tectonics based on seismic reflection, refraction and other geophysical studies

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The lithosphere (the rigid outer shell of Earth) of North America developed over the past 4 billion years to generate the collage of geological features that we now see. Determination of present lithospheric structure, and how it formed over geological time, represent basic knowledge about "inner space" that is just as important as knowledge of "outer space". Such knowledge also has practical applications: regional information useful for diamond, base metal and petroleum companies; and why and how earthquakes occur. The three proposed projects in this application provide some of this knowledge, primarily based on controlled source seismic methods. Project #1 will derive velocity structure, with higher resolution than currently possible, for the uppermost crust through application of a recently developed method, waveform tomography, to first-arriving waves on vibroseis reflection profiles. Results are interpreted in terms of rock types and may be used to improve computer processing of the full dataset. Project #2 seeks to quantitatively characterize features and develop detailed models of lithospheric boundaries, particularly for the base of the crust, the Moho, to better understand the processes involved in lithospheric development and modification. Representative models of the boundaries are generated, some based on physical models and some through statistical analyses of the properties of observed data. Synthetic data equivalent to the observed data are calculated and comparisons are made. LITHOPROBE is Canada's highly acclaimed national Earth science research project [www.lithoprobe.ca], which is concluding after 22 years. Based on results from across Canada, Project #3A will generate a 6000-km-long lithospheric cross-section from the Pacific to the Atlantic oceans as well as similar cross-sections for NW and NE Canada. These demonstrate the complexity of the processes involved in the evolution of our country. Project #3B will develop a summary of how Canada became the geological collage that it currently represents. A series of illustrations and accompanying text relating to geological domains and tectonic processes will document Canada's evolution from about 4 billion years ago to the present.