Damage amplification during repetitive seismic waves in mechanically loaded rocks
Abstract Cycles of stress build-up and release are inherent to tectonically active planets. Such stress oscillations impart strain and damage, prompting mechanically loaded rocks and materials to fail. Here, we investigate, under uniaxial conditions, damage accumulation and weakening caused by time-...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Nature Portfolio
2023-01-01
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| Series: | Scientific Reports |
| Online Access: | https://doi.org/10.1038/s41598-022-26721-x |
| _version_ | 1811175883262656512 |
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| author | Anthony Lamur Jackie E. Kendrick Lauren N. Schaefer Yan Lavallée Ben M. Kennedy |
| author_facet | Anthony Lamur Jackie E. Kendrick Lauren N. Schaefer Yan Lavallée Ben M. Kennedy |
| author_sort | Anthony Lamur |
| collection | DOAJ |
| description | Abstract Cycles of stress build-up and release are inherent to tectonically active planets. Such stress oscillations impart strain and damage, prompting mechanically loaded rocks and materials to fail. Here, we investigate, under uniaxial conditions, damage accumulation and weakening caused by time-dependent creep (at 60, 65, and 70% of the rocks’ expected failure stress) and repeating stress oscillations (of ± 2.5, 5.0 or 7.5% of the creep load), simulating earthquakes at a shaking frequency of ~ 1.3 Hz in volcanic rocks. The results show that stress oscillations impart more damage than constant loads, occasionally prompting sample failure. The magnitudes of the creep stresses and stress oscillations correlate with the mechanical responses of our porphyritic andesites, implicating progressive microcracking as the cause of permanent inelastic strain. Microstructural investigation reveals longer fractures and higher fracture density in the post-experimental rock. We deconvolve the inelastic strain signal caused by creep deformation to quantify the amount of damage imparted by each individual oscillation event, showing that the magnitude of strain is generally largest with the first few oscillations; in instances where pre-existing damage and/or the oscillations’ amplitude favour the coalescence of micro-cracks towards system scale failure, the strain signal recorded shows a sharp increase as the number of oscillations increases, regardless of the creep condition. We conclude that repetitive stress oscillations during earthquakes can amplify the amount of damage in otherwise mechanically loaded materials, thus accentuating their weakening, a process that may affect natural or engineered structures. We specifically discuss volcanic scenarios without wholesale failure, where stress oscillations may generate damage, which could, for example, alter pore fluid pathways, modify stress distribution and affect future vulnerability to rupture and associated hazards. |
| first_indexed | 2024-04-10T19:43:10Z |
| format | Article |
| id | doaj.art-7d0a7c538ec34367a1334de2f42f6556 |
| institution | Directory Open Access Journal |
| issn | 2045-2322 |
| language | English |
| last_indexed | 2024-04-10T19:43:10Z |
| publishDate | 2023-01-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | Scientific Reports |
| spelling | doaj.art-7d0a7c538ec34367a1334de2f42f65562023-01-29T12:11:25ZengNature PortfolioScientific Reports2045-23222023-01-0113111510.1038/s41598-022-26721-xDamage amplification during repetitive seismic waves in mechanically loaded rocksAnthony Lamur0Jackie E. Kendrick1Lauren N. Schaefer2Yan Lavallée3Ben M. Kennedy4Department of Earth, Ocean and Ecological Sciences, University of LiverpoolDepartment of Earth, Ocean and Ecological Sciences, University of LiverpoolU.S. Geological Survey, Geologic Hazards Science CenterDepartment of Earth, Ocean and Ecological Sciences, University of LiverpoolSchool of Earth and the Environment, University of CanterburyAbstract Cycles of stress build-up and release are inherent to tectonically active planets. Such stress oscillations impart strain and damage, prompting mechanically loaded rocks and materials to fail. Here, we investigate, under uniaxial conditions, damage accumulation and weakening caused by time-dependent creep (at 60, 65, and 70% of the rocks’ expected failure stress) and repeating stress oscillations (of ± 2.5, 5.0 or 7.5% of the creep load), simulating earthquakes at a shaking frequency of ~ 1.3 Hz in volcanic rocks. The results show that stress oscillations impart more damage than constant loads, occasionally prompting sample failure. The magnitudes of the creep stresses and stress oscillations correlate with the mechanical responses of our porphyritic andesites, implicating progressive microcracking as the cause of permanent inelastic strain. Microstructural investigation reveals longer fractures and higher fracture density in the post-experimental rock. We deconvolve the inelastic strain signal caused by creep deformation to quantify the amount of damage imparted by each individual oscillation event, showing that the magnitude of strain is generally largest with the first few oscillations; in instances where pre-existing damage and/or the oscillations’ amplitude favour the coalescence of micro-cracks towards system scale failure, the strain signal recorded shows a sharp increase as the number of oscillations increases, regardless of the creep condition. We conclude that repetitive stress oscillations during earthquakes can amplify the amount of damage in otherwise mechanically loaded materials, thus accentuating their weakening, a process that may affect natural or engineered structures. We specifically discuss volcanic scenarios without wholesale failure, where stress oscillations may generate damage, which could, for example, alter pore fluid pathways, modify stress distribution and affect future vulnerability to rupture and associated hazards.https://doi.org/10.1038/s41598-022-26721-x |
| spellingShingle | Anthony Lamur Jackie E. Kendrick Lauren N. Schaefer Yan Lavallée Ben M. Kennedy Damage amplification during repetitive seismic waves in mechanically loaded rocks Scientific Reports |
| title | Damage amplification during repetitive seismic waves in mechanically loaded rocks |
| title_full | Damage amplification during repetitive seismic waves in mechanically loaded rocks |
| title_fullStr | Damage amplification during repetitive seismic waves in mechanically loaded rocks |
| title_full_unstemmed | Damage amplification during repetitive seismic waves in mechanically loaded rocks |
| title_short | Damage amplification during repetitive seismic waves in mechanically loaded rocks |
| title_sort | damage amplification during repetitive seismic waves in mechanically loaded rocks |
| url | https://doi.org/10.1038/s41598-022-26721-x |
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