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Dilatancy and Compaction of a Rate-and-State Fault in a Poroelastic Medium: Linearized Stability Analysis

Heimisson, Elías Rafn and Rudnicki, John and Lapusta, Nadia (2021) Dilatancy and Compaction of a Rate-and-State Fault in a Poroelastic Medium: Linearized Stability Analysis. Journal of Geophysical Research. Solid Earth, 126 (8). Art. No. e2021JB022071. ISSN 2169-9313. doi:10.1029/2021jb022071.

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Faults in the crust at seismogenic depths are embedded in a fluid-saturated, elastic, porous material. Slip on such faults may induce transient pore pressure changes through dilatancy or compaction of the gouge or host rock. However, the poroelastic nature of the crust and the full coupling of inelastic gouge processes and the host rock have been largely neglected in previous analyses. Here, we present a linearized stability analysis of a rate-and-state fault at steady-state sliding in a fully-coupled poroelastic solid under in-plane and anti-plane sliding. We further account for dilatancy of the shear zone and the associated pore pressure changes in an averaged sense. We derive the continuum equivalent of the analysis by Segall and Rice (1995,, and highlight a new parameter regime where dilatancy stabilization can act in a highly diffusive solid. Such stabilization is permitted since the time scale of flux through the shear zone and diffusion into the bulk can be very different. A novel aspect of this study involves analyzing the mechanical expansion of the shear layer causing fault-normal displacements, which we describe by a mass balance of the solid constituent of the gouge. This effect gives rise to a universal stabilization mechanism in both drained and undrained limits. The importance of the mechanism scales with shear-zone thickness and it is significant for wider shear zones exceeding approximately 1 cm. We hypothesize that this stabilization mechanism may alter and delay an ongoing shear localization process.

Item Type:Article
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URLURL TypeDescription
Heimisson, Elías Rafn0000-0001-8342-7226
Rudnicki, John0000-0002-4258-8506
Lapusta, Nadia0000-0001-6558-0323
Additional Information:© 2021. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. Issue Online: 04 August 2021; Version of Record online: 04 August 2021; Accepted manuscript online: 28 June 2021; Manuscript accepted: 24 June 2021; Manuscript revised: 21 June 2021; Manuscript received: 17 March 2021. This study was supported by the Geophysics Option Postdoctoral Fellowship from the Division of Geological and Planetary Sciences at Caltech to E.R.H. and by the NSF-IUCRC Center for Geomechanics and Mitigation of Geohazards (projects GMG-4.1, GMG-4.2) to N.L. We thank reviewers Allan Rubin and Massimo Cocco for their constructive remarks and we thank Paul Segall for helpful comments. Data Availability Statement: This is a theoretical paper and contains no data. Code for determining the critical stability and solving Equation 41, which also contains explicit expressions for equations too long to write out in this paper, is found here (see Heimisson, 2021).
Group:Center for Geomechanics and Mitigation of Geohazards (GMG), Division of Geological and Planetary Sciences, Seismological Laboratory
Funding AgencyGrant Number
Caltech Division of Geological and Planetary SciencesUNSPECIFIED
Subject Keywords:Stability analysis; friction; poroelasticity; dilatancy; induced seismicity; slow slip
Issue or Number:8
Record Number:CaltechAUTHORS:20210701-172839842
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Official Citation:Heimisson, E. R., Rudnicki, J., & Lapusta, N. (2021). Dilatancy and compaction of a rate-and-state fault in a poroelastic medium: Linearized stability analysis. Journal of Geophysical Research: Solid Earth, 126, e2021JB022071.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109704
Deposited By: Tony Diaz
Deposited On:02 Jul 2021 20:13
Last Modified:15 Nov 2022 15:22

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