Synthetic seismic modelling and imaging of an impact structure

Matteo Niccoli

A geologic depth and velocity model of an impact crater was created and ray-traced. The resultant seismic data were pre- and post-stack migrated both in depth and time with the objective of evaluating which algorithm best performs in the case of a complex geologic structure, and determine which events are less well imaged. Kirchhoff migration was used in all four cases. Both pre-stack and post-stack depth migrations imaged fault planes well when contrasting lithologies were present either laterally or vertically across the planes. Both depth migrations have also well imaged the upturned layers in the central uplift. The pre-stack depth migration has better imaged deep reflectors; it has also succeeded in imaging events in the most challenging part of the section, below a complex shaped, low velocity breccia deposit. Pre-stack time migration produced superior results in terms of imaging some events, in particular the upturned layers in the central uplift. The migration, however, has performed poorly in the deep section. The post-stack time migration performed very poorly as a result of an insufficient smoothing of the migration velocity field that has affected the imaging and spread across the section. Time to depth conversion is recommended to evaluate the positioning of migrated events.