Aben, FM;
Brantut, N;
Mitchell, TM;
(2020)
Off-Fault Damage Characterization During and After Experimental Quasi-Static and Dynamic Rupture in Crustal Rock From Laboratory P Wave Tomography and Microstructures.
Journal of Geophysical Research: Solid Earth
, 125
(8)
, Article e2020JB019860. 10.1029/2020JB019860.
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Abstract
Elastic strain energy released during shear failure in rock is partially spent as fracture energy Γ to propagate the rupture further. Γ is dissipated within the rupture tip process zone, and includes energy dissipated as off-fault damage, Γ_{off}. Quantifying off-fault damage formed during rupture is crucial to understand its effect on rupture dynamics and slip-weakening processes behind the rupture tip, and its contribution to seismic radiation. Here, we quantify Γ_{off} and associated change in off-fault mechanical properties during and after quasi-static and dynamic rupture. We do so by performing dynamic and quasi-static shear failure experiments on intact Lanhélin granite under triaxial conditions. We quantify the change in elastic moduli around the fault from time-resolved 3-D P wave velocity tomography obtained during and after failure. We measure the off-fault microfracture damage after failure. From the tomography, we observe a localized maximum 25% drop in P wave velocity around the shear failure interface for both quasi-static and dynamic failure. Microfracture density data reveal a damage zone width of around 10 mm after quasi-static failure, and 20 mm after dynamic failure. Microfracture densities obtained from P wave velocity tomography models using an effective medium approach are in good agreement with the measured off-fault microfracture damage. Γoff obtained from off-fault microfracture measurements is around 3 kJ m^{2} for quasi-static rupture, and 5.5 kJ m^{2} for dynamic rupture. We argue that rupture velocity determines damage zone width for slip up to a few mm, and that shear fracture energy Γ increases with increasing rupture velocity.
| Type: | Article |
|---|---|
| Title: | Off-Fault Damage Characterization During and After Experimental Quasi-Static and Dynamic Rupture in Crustal Rock From Laboratory P Wave Tomography and Microstructures |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1029/2020JB019860 |
| Publisher version: | https://doi.org/10.1029/2020JB019860 |
| Language: | English |
| Additional information: | © 2020. The Authors. This is an open access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/). |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10106620 |
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