Short answer is seismic is better suited to sedimentary...

Short answer is seismic is better suited to sedimentary terranes. Better discrimates rapid changes in density, such as a less dense fluid trapped under an impermeable cap.

In this scenario SGQ already has SAMSON, airborne EM and gravity data and also most likely MLEM. That is a comprehensive dataset. There comes a point when it is simply uneconomic to throw the physics book at an area.

Better to test a few theories and learn something. Such as why a certain conductor might have a more rapid decay than another. Decay analysis can be related to conductance and also geology as they have different characteristics.

Someone earlier made a fantastic comment that it could be the homogenised response of two separate anomalies. Its very easy to mistake several small responses as one large one with modelling, unless you know explicitly what the geology is.

That is the inherent difficulty with potential field analysis. Non uniqueness means many solutions to one set of data.