It is proposed to acquire up to approximately 4000 km of deep crustal seismic data across the offshore Otway Basin in the period from early December 1994 to late January 1995. The principal goals of the survey (AGSO Survey 137) are to determine the deep crustal architecture of the offshore Otway Basin, to characterise the linkages between the Otway Basin and the flanking Bass Basin, Kanmantoo High and oceanic crust, and thereby to characterise the large scale extensional processes which led to the
development of the Otway Basin as part of the larger Southern Rift System. In addition, the survey is designed to test many of the newer concepts which have arisen from the interpretation of AGSO's recently acquired aeromagnetic data. The integration of the deep crustal seismic and the aeromagnetic data sets should significantly enhance our understanding of the basin architecture, as well as provide new insights into the usefulness of high resolution aeromagnetic data in sedimentary
basins. In order to constrain crustal velocities, seismic refraction data will be recorded on key lines.
In line with recent AGSO deep-seismic surveys, the Otway Basin survey will use a 4800 m streamer, configured with 192 x 25 m active groups; data will be recorded with a 16 second record length, and a 2 millisecond sample interval; the seismic source will be tuned airgun arrays with a total capacity of 49 litres, and will be fired every 50 metres to give 48-fold CDP coverage. Navigation will be by differential GPS. Using these parameters on the North West Shelf and in the Gippsland Basin, AGSO has
consistently obtained high-quality deep seismic data, with interpretable reflectors down to 8-12 s 'FWT, as well as obtaining good resolution in the upper 6 s of seismic data, which is normally the limit recorded by industry.
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