Correction to “Pore pressure and poroelasticity effects in Coulomb stress analysis of earthquake interactions” by Massimo Cocco and James R. Rice

Abstract

See, stats, and : https : / / www . researchgate . net / publication / 228793150 Correction " Pore effects earthquake " by . . . Article DOI : 10 . 1029 / 2002JB002319 CITATIONS 129 READS 96 2 : Some : EPOS - IP ENVRI+ Massimo Istituto 218 , 306 SEE James . Rice Harvard 374 , 985 SEE All . The . [ 1 ] Pore pressure changes are rigorously included in Coulomb stress calculations for fault interaction studies . These are considered changes under undrained conditions for analyzing very short term postseismic response . The assumption that pore pressure is proportional to fault - normal stress leads to the widely used concept of an effective friction coefficient . We provide an exact expression for undrained fault zone pore pressure changes to evaluate the validity of that concept . A narrow fault zone is considered whose poroelastic parameters are different from those in the surrounding medium , which is assumed to be elastically isotropic . We use conditions for mechanical equilibrium of stress and geometric compatibility of strain to express the effective normal stress change within the fault as a weighted linear combination of mean stress and fault - normal stress changes in the surroundings . Pore pressure changes are determined by fault - normal stress changes when the shear modulus within the fault zone is significantly smaller than in the surroundings but by mean stress changes when the elastic mismatch is small . We also consider an anisotropic fault zone , introducing a Skempton tensor for pore pressure changes . If the anisotropy is extreme , such that fluid pressurization under constant stress would cause expansion only in the fault - normal direction , then the effective friction coefficient concept applies exactly . We finally consider moderately longer timescales than those for undrained response . A sufficiently permeable fault may come to local pressure equilibrium with its surroundings even while that surrounding region may still be undrained , leading to pore pressure change determined by mean stress changes in those surroundings .