Laboratory Observations Linking Fault Surface Characteristics to the Onset and Evolution of Frictional Sliding and Off-fault Damage
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Date
2022-12-16
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Other Conference Item
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Abstract
The onset and evolution of frictional sliding can provide insight into processes prior to earthquake nucleation such as frictional heterogeneity imposed by variations of the asperity population. Foreshocks in nature are localized frictional instabilities prior to a mainshock. They are believed to be connected to variations in frictional strength and linked to the preparatory slow slip accumulating along the principal rupture plane prior to the mainshock. In dry and bare surfaces, the contact is established through asperities, which are topographical heights where the normal stress concentrates, hence imposing variations in fault strength. In this study, we perform triaxial tests on saw-cut Carrara Marble samples in dry and unlubricated conditions. During the tests, the frictional sample remained initially locked then transitioned to sliding. During sliding, we observed a velocity weakening phase followed by a velocity strengthening phase with increasing slip. Two types of technologies were used to study this frictional response in space and time: (1) an array of acoustic emission sensors monitored localized precursory seismicity and (2) quasi-static deformation in the fault-parallel strain was monitored using novel distributed strain sensing (DSS) using fiber optics. The high-density fault-parallel strain measurements displayed a significant heterogeneous distribution in time and space and experienced sudden reorganization at various phases of the experiment. Major strain reorganization was observed and appears to be collocated to the non-uniform wear, which appeared as grooving and off-fault damage. Worn regions exhibited high normal stress and were determined experimentally using a pressure sensitive film. These regions may explain the strain concentrations observed and potential locations of acoustic emission on the frictional interface. An accurate understanding of the stress and strain heterogeneity on and near the fault may help to improve our understanding of how precursory seismicity and aseismic preslip appear at larger scales.
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published
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American Geophysical Union
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AGU Fall Meeting 2022
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rock physics
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02818 - Schweiz. Erdbebendienst (SED) / Swiss Seismological Service (SED)
Notes
Conference lecture held on December 16, 2022.
Funding
192017 - Advancing laboratory seismology for improving the forecasting of natural and induced earthquakes (SNF)
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