Evolution of fault patterns in clay experiments

Z. Reches*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

The evolution of systems of strike-slip faults, from a single fault to intricate patterns, is examined here in a series of clay experiments. In the experiments, plates of clay are loaded laterally under constant strain rate in plane strain, with continuous monitoring of the stresses. The experiments indicate that an individual fault appears as a linear trace, about 1 mm in length, that grows by in-plane propagation of one or both ends. Next, the fault evolves by out-of-plane propagation and interacts and coalesces with other, subparallel, faults. This process generates a crooked, nonlinear fault, which at this point usually ceases to grow. Younger faults developing close to the older fault may cross and displace it. The fault pattern in a sample changes in nature during a single run. The early pattern is either domainal or conjugate, depending on the initial fault distribution. The second stage is usually domainal when subparallel faults develop close to each other. During the final stage, young faults cross old ones and generate conjugate patterns. The relation between rheology and growth mechanisms of the faults is discussed. Faults in brittle-elastic solids grow by out-of-plane propagation into zones of reduced normal stress, whereas many of the faults in the present experiments grow by in-plane propagation. This propagation direction and the fault pattern evolution, is interpreted here as indicating relaxation of nonuniform stresses at the proximity of the faults. It is further argued that stress relaxation may be applicable to faulting of rocks in the upper crust.

Original languageEnglish
Pages (from-to)141-156
Number of pages16
JournalTectonophysics
Volume145
Issue number1-2
DOIs
StatePublished - 2 Jan 1988

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