Regresar

Integrated PSDM and simulated annealing optimization for decollement 2D quantitative imaging

Abstract:

To analyse the physical properties of seismic reflectors as possible indicators of the presence of fluids, we develop an improvement of our previous work based on conventional preserved amplitude prestack depth migration/inversion (PSDM) coupled with a specific post-processing of the tomographic model. The specific post-processing sequence allows us to: (1) eliminate effects of limited source bandwith and source-receiver aperture range; (2) obtain the absolute values of the seismic attributes; (3) obtain the correct geometry of seismic reflectors reaching the theoretical seismic resolution of the source wavelet. Unlike our previous work, during the post-processing sequence the model space exploration is made automatically via a random search, and optimal models are determined using the very fast simulated annealing algorithm. We present an application to multichannel seismic reflection data to obtain 2-dimensional quantitative imaging of the decollement on a profile located on the Ecuadorian margin. Preliminary results suggest that the decollement corresponds to a layer of a thickness of 80 meters and with a negative velocity perturbation around -50 m/s that can reach locally values down to -150m/s. Along the decollement we can observe regions with a relative velocity decrease due to the variations of the physical properties between the subducted sediments and the overriding plate materials above the decollement. The relative velocity decrease can be probably associated with the change in fluid pressure.