Walkway VSP surveys obtained of coal strata near Red Deer demonstrate good quality compressional and converted-wave imaging of the coal zone. Reflectivity analysis of the top of coal reflection demonstrates that PP reflectivity values differ substantially from those predicted by single-interface numerical modelling. Detailed numerical modelling, including several interfaces within the coal zone as well as the base of coal reflection yields predicted reflectivity values much nearer those extracted from field data, and result from thin-bed tuning. PS reflectivity values, however, match those predicted by single-interface numerical modelling well, indicating that they are less affected by tuning effects than the PP reflectivity values.
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