Time-dependent weakening of granite at hydrothermal conditions
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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.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Time-dependent weakening of granite at hydrothermal conditions |
| Series title | Geophysical Research Letters |
| DOI | 10.1029/2023GL105517 |
| Volume | 50 |
| Issue | 21 |
| Year Published | 2023 |
| Language | English |
| Publisher | American Geophysical Union |
| Contributing office(s) | Earthquake Science Center |
| Description | e2023GL105517, 9 p. |
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