Advancing Waveform Tomography of Crosswell Data with Applications in the Sulphide Environment
Crosswell seismic tomography is a geophysical survey method in which the propagation of sound waves through the Earth’s crust is used to infer geological structure. An array of acoustic sources and receivers are placed into two separate boreholes, and full waveform recordings are made of the response to each source, measured at each of the receivers, the objective being a ―cross-section‖ of the geology between the two boreholes. Two attributes are extracted from this survey: i) the measured arrival times, and ii) the frequency domain components of the waveforms. Traveltime tomography is used initially to image crosssectional structure by examining the times at which the receivers first detect seismic waves generated by the sources, allowing a model of variable seismic velocity to be created.
Waveform tomography then uses the frequency domain components to improve the model resolution by taking into account the scattering and distortion of seismic waves at different frequencies. Computer software developed by the University of Western Ontario is used to create these models, which are useful in commercial geophysical exploration (for economic ores, oil & gas, etc.). Specifically for this project, data from Vale Voisey’s Bay property in Labrador will be examined.