Fault rock heterogeneity can produce fault weakness and reduce fault stability

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Authors

John Bedford, Daniel Faulkner, Nadia Lapusta

Abstract

Geological heterogeneity is abundant in crustal fault zones; however, its role in controlling the mechanical behaviour of faults is poorly constrained. Here, we present laboratory friction experiments on laterally heterogeneous faults, with patches of strong, rate-weakening quartz gouge and weak, rate-strengthening clay gouge. The experiments show that the heterogeneity leads to a significant reduction in strength and frictional stability in comparison to compositionally identical faults with homogeneously mixed gouges. We identify a combination of weakening effects, including smearing of the weak clay; differential compaction of the two gouges redistributing normal stress; and shear localization producing stress concentrations in the strong quartz patches. The results demonstrate that geological heterogeneity and its evolution can have pronounced effects on fault strength and stability and, by extension, on the occurrence of slow-slip transients versus earthquake ruptures and the characteristics of the resulting events, and should be further studied in lab experiments and earthquake source modelling.

DOI

https://doi.org/10.31223/X51P6W

Subjects

Earth Sciences, Geology, Geophysics and Seismology, Tectonics and Structure

Keywords

Fault

Dates

Published: 2021-08-30 05:06

Last Updated: 2021-10-08 05:32

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License

CC BY Attribution 4.0 International

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