Pore fluid pressure, apparent friction, and Coulomb failure

Journal of Geophysical Research B: Solid Earth
By: , and 



Many recent studies of stress-triggered seismicity rely on a fault failure model with a single free parameter, the apparent coefficient of friction, presumed to be a material constant with possible values 0 ≤ μ′ ≤ 1. These studies may present a misleading view of fault strength and the role of pore fluid pressure in earthquake failure. The parameter μ′ is intended to incorporate the effects of both friction and pore pressure, but is a material constant only if changes in pore fluid pressure induced by changes in stress are proportional to the normal stress change across the potential failure plane. Although specific models of fault zones permit such a relation, neither is it known that fault zones within the Earth behave this way, nor is this behavior expected in all cases. In contrast, for an isotropic homogeneous poroelastic model the pore pressure changes are proportional to changes in mean stress, μ′ is not a material constant, and −∞ ≤ μ′ ≤ +∞. Analysis of the change in Coulomb failure stress for tectonically loaded reverse and strike-slip faults shows considerable differences between these two pore pressure models, suggesting that such models might be distinguished from one another using observations of triggered seismicity (e.g., aftershocks). We conclude that using the constant apparent friction model exclusively in studies of Coulomb failure stress is unwise and could lead to significant errors in estimated stress change and seismic hazard.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Pore fluid pressure, apparent friction, and Coulomb failure
Series title Journal of Geophysical Research B: Solid Earth
DOI 10.1029/2000JB900119
Volume 105
Issue B11
Year Published 2000
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Geophysical Research B: Solid Earth
First page 25533
Last page 25542
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