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Dehydration‐induced instabilities at intermediate depths in subduction zones
Author(s) -
Brantut Nicolas,
Stefanou Ioannis,
Sulem Jean
Publication year - 2017
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2017jb014357
Subject(s) - instability , geology , subduction , compaction , pressure solution , slab , porosity , pore water pressure , deformation (meteorology) , yield (engineering) , nucleation , strain rate , dehydration reaction , dehydration , geotechnical engineering , mechanics , thermodynamics , materials science , seismology , geophysics , composite material , tectonics , chemistry , oceanography , physics , biochemistry
We formulate a model for coupled deformation and dehydration of antigorite, based on a porosity‐dependent yield criterion and including shear‐enhanced compaction. A pore pressure and compaction instability can develop when the net volume change associated with the reaction is negative, i.e., at intermediate depth in subduction zones. The instability criterion is derived in terms of the dependence of the yield criterion on porosity: if that dependence is strong, instabilities are more likely to occur. We also find that the instability is associated with strain localization, over characteristic length scales determined by the hydraulic diffusivity, the elasto‐plastic parameters of the rock, and the reaction rate. Typical lower bounds for the localization length are of the order of 10 to 100 for antigorite dehydration and deformation at 3 GPa. The fluid pressure and deformation instability is expected to induce stress buildup in the surrounding rocks forming the subducted slab, which provides a mechanism for the nucleation and propagation of intermediate‐depth earthquakes.