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Abstract The material properties and distribution of faults above the seismogenic zone promote or inhibit earthquake rupture propagation. We document the depths and mechanics of fault slip along the seismically active Hurricane fault, UT, with scanning and transmission electron microscopy and hematite (U‐Th)/He thermochronometry. Hematite occurs as mm‐scale, striated patches on a >10 m2thin, mirror‐like silica fault surface. Hematite textures include bulbous aggregates and cataclasite, overlain by crystalline Fe‐oxide nanorods and an amorphous silica layer at the slip interface. Textures reflect mechanical, fluid, and heat‐assisted amorphization of hematite and silica‐rich host rock that weaken the fault and promote rupture propagation. Hematite (U‐Th)/He dates document episodes of mineralization and fault slip between 0.65 and 0.36 Ma at ∼300 m depth. Data illustrate that some earthquake ruptures repeatedly propagate along localized slip surfaces in the shallow crust and provide structural and material property constraints for in models of fault slip.
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Shear‐induced amorphization in boron subphosphide (B 12 P 2 ): Direct transition versus stacking fault mediation
Abstract The shear‐induced amorphization has been observed in many strong ceramics and is responsible for their cracking and fragmentation. But its underlying mechanism remains elusive due to the complex structure and bonding environment in strong ceramics. To illustrate the deformation mechanism of local amorphization in strong ceramics, we employed molecular dynamics simulations with a deep‐learning force field to examine the shear‐induced amorphization in B12P2. Surprisingly, we identified a stacking‐fault‐mediated amorphization mechanism along the most plausible slip system (1 1 1)/[1 1 ]. This mechanism is even more favorable at a higher temperature than room temperature. In contrast, the direct crystal to amorphization transition, due to the icosahedral slip, is observed for the other most plausible slip system (0 1 1)/[2 ]. We report the activation volume and the activation free energy for the amorphization along the (1 1 1)/[1 1 ] slip system. The derived activation volume is only 41.47 A3, which is roughly 2–3 icosahedra, suggesting that the localized amorphization in B12P2is mediated by stacking fault formation. The previous results suggest complex amorphization mechanisms in strong ceramics.
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- Award ID(s):
- 1727428
- PAR ID:
- 10370534
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of the American Ceramic Society
- Volume:
- 105
- Issue:
- 11
- ISSN:
- 0002-7820
- Page Range / eLocation ID:
- p. 6826-6838
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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