DOI: 10.5061/dryad.2v6wwpzvr
title: Data from: Friction and instability of glaucophane gouges at blueschist temperatures support abundance of intermediate-depth earthquakes

description: Fluid release from the hydraulically-confined dehydration of blueschist
 minerals may significantly elevate fluid pressures and concomitantly
 reduce effective stresses. This is a viable mechanism to explain brittle
 failure and frictional instability, and it is a possible explanation for
 intermediate-depth earthquakes in cold subduction zones. We examine this
 hypothesis for glaucophane – a key index mineral for blueschist facies –
 at lower confining stresses where behavior is poorly understood. We
 conduct laboratory shear tests on glaucophane gouge at temperatures of
 100–500℃ and effective normal stresses of 50–200 MPa, to explore the
 controls of temperature, stresses and excess pore fluid pressures on fault
 friction. Frictional strength of glaucophane gouge at representative
 temperatures and stresses is ~0.70 and insensitive to temperature with a
 slight increase in friction coefficient at lower effective stresses.
 Elevating temperature promotes a transition from velocity-strengthening to
 mild velocity-weakening behavior, indicating the destabilizing effect of
 high-temperature downdip in subduction zones. Reducing effective normal
 stress or concomitantly elevating pore fluid pressure, potentially sourced
 from dehydration reactions, further strengthens the velocity-weakening
 response and would be manifest as moderate-sized earthquakes. This
 observed instability at higher temperatures or lower stresses is indexed
 with and accompanied by denser distributions of strongly- to
 moderately-localized shears in the microstructures – congruent with the
 observed mechanical response. Our results support the potential for
 enhanced unstable sliding of glaucophane gouges at lower effective
 stresses and at blueschist facies temperatures - and have significant
 implications for understanding the abundance of intermediate-depth
 earthquakes apparent in cold subduction zones.
description: # Data from: Friction and instability of glaucophane gouges at blueschist
 temperatures support abundance of intermediate-depth earthquakes
 **Data S1** The
 friction-displacement data for the eight shear experiments on glaucophane
 gouge. **File lists (files found within DataS1.zip)**
 An_et_al_2023_Gla_T100.xlsx An_et_al_2023_Gla_T200.xlsx
 An_et_al_2023_Gla_T300.xlsx An_et_al_2023_Gla_T400.xlsx
 An_et_al_2023_Gla_T500.xlsx An_et_al_2023_Gla_T300_E100.xlsx
 An_et_al_2023_Gla_T300_E50.xlsx An_et_al_2023_Gla_T300_P80.xlsx **File
 description** An_et_al_2023_Gla_T100.xlsx – The shear displacement (column
 1) and coefficient of friction (column 2) data for Experiment Gla-T100.
 An_et_al_2023_Gla_T200.xlsx – The shear displacement (column 1) and
 coefficient of friction (column 2) data for Experiment Gla-T200.
 An_et_al_2023_Gla_T300.xlsx – The shear displacement (column 1) and
 coefficient of friction (column 2) data for Experiment Gla-T300.
 An_et_al_2023_Gla_T400.xlsx – The shear displacement (column 1) and
 coefficient of friction (column 2) data for Experiment Gla-T400.
 An_et_al_2023_Gla_T500.xlsx – The shear displacement (column 1) and
 coefficient of friction (column 2) data for Experiment Gla-T500.
 An_et_al_2023_Gla_T300_E100.xlsx – The shear displacement (column 1) and
 coefficient of friction (column 2) data for Experiment Gla-T300-E100.
 An_et_al_2023_Gla_T300_E50.xlsx – The shear displacement (column 1) and
 coefficient of friction (column 2) data for Experiment Gla-T300-E50.
 An_et_al_2023_Gla_T300_P80.xlsx – The shear displacement (column 1) and
 coefficient of friction (column 2) data for Experiment Gla-T300-P80.