The South Ecuador subduction channel: evidence for a dynamic mega-shear zone from 2D fine-scale seismic reflection imaging, implications for material transfer - Université Pierre et Marie Curie Accéder directement au contenu
Article Dans Une Revue Journal of Geophysical Research Année : 2011

The South Ecuador subduction channel: evidence for a dynamic mega-shear zone from 2D fine-scale seismic reflection imaging, implications for material transfer

Jean-Yves Collot
  • Fonction : Auteur
Alessandra Ribodetti
  • Fonction : Auteur
Françoise Sage
  • Fonction : Auteur
W. Agudelo
  • Fonction : Auteur

Résumé

Tectonic processes that control the transition from poorly consolidated sediment entering the subduction channel (SC) to the seismogenic zone are documented using seismic imaging. We applied pre-stack depth migration and a post-processing sequence to a seismic reflection line acquired across the Ecuador convergent margin to obtain a 2D-quantitative image of the first ∼24 km of the SC. Structural interpretation shows that the SC consists of a 630-1150-m-thick, low-velocity, continuous sheet of sediment that dips ∼6° landward and undergoes shear deformation. The long sheet is bounded at top and bottom by décollement thrusts, and developed over time Riedel shears and basal thrust faulting and folding downdip, pointing to a dynamic mega-shear zone. Modeling the strong uppermost and basal SC reflectors reveals that they are associated with 40-80-m-thick, 50-350 m/s, low-velocity perturbations layers inferred to be fluid rich and mechanically weak. A fine-scale velocity model shows two anomalously low-Vp areas in the long sheet, advocating patches of over-pressured fluids. Evidence for Vp variations along the upper-plate foundation suggests either underplated bodies or a fluid-damage zone. A simple temporal reconstruction indicates that underthrusting the long sheet initiated >450 kyr ago and interrupted ∼54 ± 13 kyr ago, when frontal accretion resumed. During this transient evolution, the SC boundaries revealed highly unstable as most of the SC was underplated while down going plate material may have been sheared off and incorporated to the SC.
Fichier principal
Vignette du fichier
2011JB008429.pdf (7.76 Mo) Télécharger le fichier
Origine : Fichiers éditeurs autorisés sur une archive ouverte

Dates et versions

hal-00653256 , version 1 (25-10-2021)

Licence

Copyright (Tous droits réservés)

Identifiants

Citer

Jean-Yves Collot, Alessandra Ribodetti, Françoise Sage, W. Agudelo. The South Ecuador subduction channel: evidence for a dynamic mega-shear zone from 2D fine-scale seismic reflection imaging, implications for material transfer. Journal of Geophysical Research, 2011, 116, pp.B11102. ⟨10.1029/2011JB008429⟩. ⟨hal-00653256⟩
58 Consultations
14 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More