Modelling seismic reflections in central Australia by the 3D isochronal technique

Abstract

A simple and efficient 3D isochronal modelling technique has been developed to study elastic wave reflections with full inclusion of diffractions. This modelling technique employs an integral representation of reflections from a surface or a scatterer. High frequency asymptotic approximations are used for the propagation between the seismic source or receiver and a surface or a scatterer. At a scattering region, first order approximations are assumed. With these approximations, the reflected seismograms are calculated by convolving the time derivative of a source function with a model weight function for a particular source-receiver pair. The weight function at a time is evaluated by a line integral along a contour on a reference surface for which the total travel time from source to receiver via the contour is equal to the time. The modelling technique can be used to study the validity of seismic interpretations by comparing observed data with synthetic data calculated from interpreted models. If the resemblance between the observed and calculated data is strong, it is likely that the interpretation is correct. Here, the modelling technique is used to investigate the nature of reflected energies from the Gardiner Fault and the Redbank Thrust Zone and also to model possible structures to explain the seismic responses observed at the base of the Amadeus Basin sequences. Thus, we hope to achieve better understanding of the structure of the basin in central Australia.