Application of a Recently Developed Inversion Procedure to Seismic Data from the Gippsland Basin

A seismic inversion procedure has been developed that inverts data available from an unmigrated stacked section to produce an interval velocity model. The stacking velocity information is not used directly but incorporated in the determination of two-way reflection times for the offset rays believed to have greatest influence in the initial determination of the stacking velocities. This modification addresses the problem of non-hyperbolic moveout curves. The use of a generalized linear inversion technique addresses another difficulty inherent in many existing interval velocity modelling methods: velocity errors cumulative with depth. Lateral variations in the interval velocity are also permitted in our procedure.

The inversion procedure is applied to seismic data from the Gippsland Basin. At each location of interest, the input data consists of three stacking velocities and five horizon times per layer. The output from the inversion procedure consists of three depths, the interval velocity and the interval velocity gradient for each layer.

A significant reduction in the data mismatch is found relative to earlier results in which the moveout curves were assumed to be hyperbolic. This indicates that our treatment of stacking velocities is more appropriate when analysing the velocity structure of such regions.