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Time-dependent weakening of granite at hydrothermal conditions

November 13, 2023

The evolution of a fault's frictional strength during the interseismic period is a critical component of the earthquake cycle, yet there have been relatively few studies that examine the time-dependent evolution of strength at conditions representative of seismogenic depths. Using a simulated fault in Westerly granite, we examined how frictional strength evolves under hydrothermal conditions up to 250°C during slide-hold-slide experiments. At temperatures ≤100°C, frictional strength generally increases with hold duration but, at 200 and 250°C, an initial increase in strength transitions to rapid time-dependent weakening for holds longer than 14 hr. Forward modeling of long hold periods at 250°C using the rate and state friction constitutive equations requires a second, strongly negative, state variable with a long evolution distance. This implies that significant hydrothermal alteration is occurring at 250°C, consistent with microstructural observations of dissolution and secondary mineral precipitation.

Publication Year 2023
Title Time-dependent weakening of granite at hydrothermal conditions
DOI 10.1029/2023GL105517
Authors Tamara Nicole Jeppson, David A. Lockner, Nicholas M. Beeler, Diane E. Moore
Publication Type Article
Publication Subtype Journal Article
Series Title Geophysical Research Letters
Index ID 70250652
Record Source USGS Publications Warehouse
USGS Organization Earthquake Science Center