Time‐Dependent Weakening of Granite at Hydrothermal Conditions

Journal Article · 13 November 2023 · Geophysical Research Letters

DOI: https://doi.org/10.1029/2023GL105517 · OSTI ID:2205540

Jeppson, T. N.  ^[1]; Lockner, D. A.  ^[1]; Beeler, N. M.  ^[1]; Moore, D. E.  ^[1]

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1. U.S. Geological Survey Earthquake Science Center Menlo Park CA USA

Abstract 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.

• Sponsoring Organization: USDOE
• OSTI ID: 2205540
• Alternate ID(s): OSTI ID: 2263267
• Journal Information: Geophysical Research Letters, Journal Name: Geophysical Research Letters Vol. 50 Journal Issue: 21; ISSN 0094-8276
• Publisher: American Geophysical Union (AGU)Copyright Statement
• Country of Publication: United States
• Language: English