A broadside and end-on seismic experiment on the crustal structure of the Newfoundland Appalachians

Roberts, Brian J. (1998) A broadside and end-on seismic experiment on the crustal structure of the Newfoundland Appalachians. Masters thesis, Memorial University of Newfoundland.

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Abstract

A special broadside and wide-angle seismic experiment was conducted in central Newfoundland in order to test the feasibility of obtaining meaningful information on the true dip of reflectors and amplitude-offset relationships in a small area of psuedo-3D coverage. -- The analysis of the data from this experiment involved producing 2D and 3D seismic images from the broadside shots, and producing a 2D section from the end-on-south shots. Also, an amplitude versus offset analysis (AVO) was completed on deep crustal reflections using the end-on-south shots. The seismic images have been interpreted in terms of the regional geological structures and correlated with the results from regional seismic reflection and refraction surveys. -- It is determined that the quality of the low fold 2D sections produced using the wide-angle shots compares favourably with that of the high fold regional lines. The interpretation of the 3D volume was problematical, leading to recommendations for better 3D survey design: however, three horizons have been mapped and time structure maps display their 3D orientation. It is determined that information on the true dip of reflectors along the regional lines can be provided using the relatively inexpensive broadside shots. The AVO results fail to provide conclusive results for changes in Poisson's ratio across any of the major reflecting interfaces in the area of the broadside experiment in central Newfoundland. If the statisical trends can be trusted, a decrease in Poisson's ratio at the top of the lower crust is indicated, however a firm value cannot be placed on this decrease. The AVO results are ambiguous probably because of seismic scattering due to a high degree of lateral inhomogeneity in the crystalline crust.

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