2D fine-scale imaging of the subduction channel in Gulf of Guayaquil by integrated iterative PSDM and simulated annealing optimization

Description

To analyze the physical properties of seismic reflectors as possible indicators of the presence of fluids, we apply a processing sequence based on preserved amplitude prestack depth migration/inversion (PSDM) coupled with a post-processing of the depth migrated image. Aim of the post-processing is to remove the effects of the limited source bandwidth, that is, to build a structural velocity model and an impulsional migrated section from the limited-bandwidth migrated image and to estimate the uncertainties of velocities and layer thicknesses.We present here an application of this depth-domain processing sequence to a 2D multichannel seismic reflection dataset for the study of the décollement reflector in the Gulf of Guayaquil (Ecuadorian margin). Preliminary results show that the décollement mainly corresponds to a layer of 80–100 meters in thickness with a mean and maximum negative velocity contrasts of −50 m/s and −150m/s respectively on top of it. Along the décollement, these negative velocity contrasts result from the contrast in the physical properties between the subducted sediments and the overriding plate materials above the décollement. Very likely, this velocity decrease is also associated with changes in fluid pressure.

Abstract

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