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Short-term deformation of accretionary prism, the role of mechanical and thermal inheritance. Application to Makran

Abstract : Makran has a largely unconstrained seismogenic potential although GPS data indicate the subduction is accumulating some strain to be released during future earthquakes. I first build a structural map along the Iranian part of the Oman Sea which indicates three segments. Then, I retrieve the pore fluid pressure and the frictional properties of the wedge with the critical taper theory and the limit analysis. The results show that along the eastern and western profiles, a transition from very low to extremely low friction is required to activate the large coastal normal fault. To propagate the deformation to the front, an increase of friction along the imbricated zone is necessary.The Makran Models are calibrated the thermal parameters and boundary conditions of the numerical simulations using seafloor and bottom sea reflector depth and few available well data. Considering two décollements, the results show that, -underplating is associated to viscous deformation -dewatering and smectite/illite transition permit to produce three slope segments observed in accretionary prisms but this friction drop is not sufficient for formation of normal faults. - the subduction of a large seamount is accompanied by large normal faults, while their location migrates through time. If the brittle décollements have a seismogenic behavior, the down-dip limit of the seismogenic zone will correspond to the onset of underplating. By assuming that the up-dip limit of seismic asperities correlates with smectite-illite transition, then a seismic asperity may extend from this transition, down to the onset of underplating, and correlate with a relatively flat topography.
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Submitted on : Thursday, July 21, 2022 - 3:24:14 PM
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  • HAL Id : tel-03735673, version 1

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Sepideh Pajang. Short-term deformation of accretionary prism, the role of mechanical and thermal inheritance. Application to Makran. Earth Sciences. Sorbonne Université; Université de Birjand (République islamique d'Iran ; 1975-..), 2021. English. ⟨NNT : 2021SORUS483⟩. ⟨tel-03735673⟩

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