Off-Fault Plasticity Influence on Rupture Dynamics and Ground Motions
Abstract
A fractured medium, such as a damage zone surrounding a fault, cannot behave fully elastically, but rather plastically. We perform 2D and 3D dynamic rupture simulations in such a medium, inside which the shear stresses are bounded. We computed the 2D in-plane, anti-plane, and, for the first time, more realistic 3D geometries. Some general features hold in all cases. Compared to the full elasto-dynamic case, the slip velocity is now bounded, the rupture speed is slightly decreased, and the overall final slip shape shows differences. The energy lost outside the fault increases linearly with the rupture propagation length. This energy is dissipated close to the crack tip, and hence has a lot of consequences on the energy balance of the rupture. We show that the rupture cannot break barriers as easily as a pure elastic crack does, favoring the spontaneous arrest of the rupture. The plasticity stabilizes the rupture instability, scaling the fracture energy with the growing size of the crack.Taking this phenomenon into account for earthquakes should lead to reduce the spatial variability of the fracture energy, that is usually needed to stop the rupture. We also show that the plasticity reduces the high frequency content of ground motions. Close to the fault, it does reduce the peak ground velocity and peak ground acceleration by several tens of percents.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.S43E..02H
- Keywords:
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- 7209 Earthquake dynamics (1242)