Volumetric and shear processes in crystalline rock approaching faulting
| Autor: | Paul Meakin, Yehuda Ben-Zion, Neelima Kandula, Benoit Cordonnier, François Renard, Jessica McBeck |
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| Rok vydání: | 2019 |
| Předmět: |
Coalescence (physics)
Multidisciplinary 010504 meteorology & atmospheric sciences 010502 geochemistry & geophysics Overburden pressure 01 natural sciences Stress field Shear (sheet metal) Brittleness Compressive strength Physical Sciences Petrology Differential stress Geology Microscale chemistry 0105 earth and related environmental sciences |
| Zdroj: | Proceedings of the National Academy of Sciences of the United States of America. 116(33) |
| ISSN: | 1091-6490 0027-8424 |
| Popis: | Understanding the approach to faulting in continental rocks is critical for identifying processes leading to fracturing in geomaterials and the preparation process of large earthquakes. In situ dynamic X-ray imaging and digital volume correlation analysis of a crystalline rock core, under a constant confining pressure of 25 MPa, are used to elucidate the initiation, growth, and coalescence of microfractures leading to macroscopic failure as the axial compressive stress is increased. Following an initial elastic deformation, microfractures develop in the solid, and with increasing differential stress, the damage pervades the rock volume. The creation of new microfractures is accompanied by propagation, opening, and closing of existing microfractures, leading to the emergence of damage indices that increase as powers of the differential stress when approaching failure. A strong spatial correlation is observed between microscale zones with large positive and negative volumetric strains, microscale zones with shears of opposite senses, and microscale zones with high volumetric and shear strains. These correlations are attributed to microfracture interactions mediated by the heterogeneous stress field. The rock fails macroscopically as the microfractures coalesce and form a geometrically complex 3D volume that spans the rock sample. At the onset of failure, more than 70% of the damage volume is connected in a large fracture cluster that evolves into a fault zone. In the context of crustal faulting dynamics, these results suggest that evolving rock damage around existing locked or future main faults influences the localization process that culminates in large brittle rupture events. |
| Databáze: | OpenAIRE |
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