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Evolution of shear fabric in granular fault gouge from stable sliding to stick slip and implications for fault slip mode
Author(s)
Language
English
Obiettivo Specifico
2IT. Laboratori sperimentali e analitici
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
8/45 (2017)
Pages (printed)
731–734
Issued date
August 2017
Abstract
Laboratory and theoretical studies provide insight into the mechanisms that control earthquake nucleation, when fault slip velocity is slow (<0.001 cm/s), and dynamic rupture when fault slip rates exceed centimeters per second. The application of these results to tectonic faults requires information about fabric evolution with shear and its impact on the mode of faulting. Here we report on laboratory experiments that illuminate the evolution of shear fabric and its role in controlling the transition from stable sliding (v ∼0.001 cm/s) to dynamic stick slip (v > 1 cm/s). The full range of fault slip modes was achieved by controlling the ratio K = k/kc, where k is the elastic loading stiffness and kc is the fault zone critical rheologic stiffness. We show that K controls the transition from slow-and-silent slip (K > 0.9) to fast-and-audible (K < 0.7, v = 3 cm/s, slip duration 0.003 s) slip events. Microstructural observations show that with accumulated strain, deformation concentrates in shear zones containing sharp shear planes made of nanoscale grains, which favor the development of frictional instabilities. Once this fabric is established, fault fabric does not change significantly with slip velocity, and fault slip behavior is mainly controlled by the interplay between the rheological properties of the slipping planes and fault zone stiffness.
Type
article
File(s)
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731.pdf
Description
manuscript in pdf
Size
2.65 MB
Format
Adobe PDF
Checksum (MD5)
530144af91333e97fe3c43d610636aeb