F. J. Taylor’s research while affiliated with Mineral Resources, The Commonwealth Scientific and Industrial Research Organisation and other places

An expanding reflection spread with a maximum shot-receiver offset of 25 km was recorded in the Missionary Plain region to obtain seismic velocity estimates throughout the crust. Although there are lateral variations in seismic velocities and a small northerly dip of the sedimentary rocks, useful average interval velocities for each sedimentary formation were derived from measured reflection times. Below depths of 3 km, these interval velocities are a significant improvement on those obtainable from industry or Bureau of Mineral Resources (BMR) near-vertical incidence reflection data. The results enable more reliable estimates of the thickness of the deeper sedimentary formations to be derived. Refracted arrivals from the expanding spread were used to define seismic velocities at depths less than 1.5 km where there are few clear reflectors.

An expanding reflection spread with a maximum shot-receiver offset of 25 km was recorded in the northern part of the Amadeus Basin, Central Australia, to obtain seismic velocity estimates throughout the crust. Arrival times of reflections indicate significant lateral variations in P-wave velocities superimposed on the small northerly dip of the sedimentary sequence. Nevertheless, a useful velocity profile that contains two pronounced low velocity zones has been derived for the basin sedimentary rocks to depths of 8.6 km. Below depths of 3 km, these interval velocities are a considerable improvement on those obtainable by standard velocity analysis techniques on the coincident near-vertical incidence reflection data; the results thus enable the determination of more reliable estimates of the thicknesses of the deeper sedimentary formations. The refracted arrivals from the expanding spread yield well-constrained P-wave velocities for shallow depths, but below about 1.5 km depth, the refraction interpretation is problematic owing to the absence of a refracted arrival through the high velocity lid in the interval velocities at depths between 1.8 and 2.7 km. The determination of useful velocity estimates for basement rocks is hampered by the presence of peg-leg multiples produced within the overlying sedimentary formations.