Seismic Damage Zones and Their Impact within Thrust and Fault Imaging

3D reflection seismic data provide interpreters with the ability to map structures and stratigraphic features in 3D detail to a resolution of a few tens of meters over thousands of square kilometers. Despite these great advances still great uncertainty exists as to the patterns of deformation that develop within deep water submarine thrust belts. While the superficial structure and spacing of major folds may be visible, in most cases the trajectory of thrust faults is highly conjectural. Even where seismic data are excellent, structural interpretations conventionally define thrusts by breaks and apparent offsets of seismic reflectors. Yet this may not be sufficient to identify the position of thrusts, their associated splays and the zones of damaged wall-rocks. Finally many interpretations rely on theoretical “end-member” behaviors of thrust geometry where concept as strain localization or mechanics of multilayer are for simplicity avoided and outcrop studies indicate that such descriptions are unsatisfactory. In order to fill these gaps and improve the 3D visualization of such deep water structures, in addition to the conventional mapping of reflector amplitudes, here we use seismic attributes mapping that uses variations in the amplitude and phase of the seismic wavelet and tracks these through entire data volumes. In general seismic attributes improve the signal interpretation and are calculated and applied to entire 3-D post-stack seismic volumes.

By showing clear 3D seismic example from Deep water structures and accretionary prism system we indicate how 3D seismic image processing methods can map strain and damage through amplitude/phase properties of the seismic signal revealing narrow thrusts, plus distributed faulting and strain called "Seismic damage Zones". Moreover within accretionary prims the seismic image processing fine tune the main seismogenetic structures and highlight the main fluid pathways. This is done by quantifying and delineate the short-range anomalies on the intensity of reflector amplitudes and collecting these into "disturbance geobodies”.

This seismic image processing method represents a first efficient step toward a construction of robust techniques to investigate sub-seismic strain and displacement within subsurface geology.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California