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- Title
Experimental Insights Into Fault Reactivation and Stability of Carrara Marble Across the Brittle–Ductile Transition.
- Authors
Niu, Lu; Zhou, Yongsheng; Shao, Tongbin; Wang, Lei; Xu, Xiwei; Rybacki, Erik
- Abstract
Little is known about the impact of pressure (P) and temperature (T) on faulting behavior and the transition to fault locking under high P–T conditions. Using a Paterson gas‐medium apparatus, triaxial compression experiments were conducted on Carrara marble (CM) samples containing a saw‐cut interface at ∼40° to the vertical axis at a constant axial strain rate of ∼1 × 10−5 s−1, P = 30–150 MPa and T = 20–600°C. Depending on the P–T conditions, we observed the complete spectrum of deformation behavior, including macroscopic (shear) failure, stable sliding, unstable stick‐slip, and bulk deformation with locked faults. Macroscopic failure and stable sliding were limited to P < 100 MPa and T = 20°C. In contrast, at P ≥ 100 MPa or T ≥ 500°C, faults were locked, and samples with bulk deformation experienced strain hardening at strains ≤8.8%. At T = 100–400°C and P ≤ 100 MPa, we observed unstable stick‐slip behavior, where both fault reactivation stress and subsequent stress drop increased with increasing pressure and temperature, associated with increasing matrix deformation and less fault slip. Microstructures indicate a mixture of microcracking, twinning and dislocation activity (e.g., kinking and undulatory extinction) that depends on P–T conditions and peak stress. The transition from slip to lock‐up with increasing pressure and temperature is induced by an enhanced contribution of crystal plastic deformation. Our results show that fault reactivation and stability in CM are significantly influenced by P–T conditions, probably limiting the nucleation of earthquakes to a depth of a few kilometers in calcite‐dominated faults. Plain Language Summary: The nucleation depth of natural earthquakes is often limited to a certain depth range that depends on lithology and environmental conditions (e.g. T and P). Here, we performed an experimental study on Carrara marble with saw‐cut and polished faults in a triaxial deformation apparatus at pressures up to 150 MPa and temperatures up to 600°C to investigate the conditions under which the fault is reactivated or already locked. Due to an increasing amount of plastic deformation with increasing temperature and pressure, the deformation of the pre‐faulted rock partitions increasingly into enhanced matrix deformation and less fault slip, associated with higher reactivation stress and larger stress drops. Extrapolating our laboratory results to natural calcite‐dominated faults suggests that earthquakes may occur at depths of a few kilometers. At greater depths, faults are likely locked, and calcite rocks dominantly deform in the ductile regime. Key Points: Deformation mode from stable sliding to stick‐slip and to fault locking was observed in triaxial tests on saw‐cut Carrara marbleFault reactivation stress and associated stress drop magnitude in the unstable regime increase with pressure and temperatureReactivation of a calcite‐dominated fault in nature may be expected down to ∼4–6 km depth
- Subjects
STRAIN hardening; MATERIAL plasticity; STRAINS &; stresses (Mechanics); STRAIN rate; MARBLE; BOLTED joints
- Publication
Journal of Geophysical Research. Solid Earth, 2024, Vol 129, Issue 4, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2023JB028364