Friction and instability of glaucophane gouges at blueschist temperatures support abundance of intermediate-depth earthquakes

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..., , , # 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...