Integrating Grain-Scale and Fault-Scale Geomechanical Models: A Multi-Scale Study of Fault Triggering
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Observations have shown that minor changes in the stress state of faults can be significant enough to induce seismic slip. One source of these minor stress changes is from naturally occurring earthquakes located several fault dimensions away from the triggered fault. The seismic waves generated can induce a cascade of other earthquakes as they pass through the crust, however, the details of this process are not understood. The current study uses a dynamic rupture model – a powerful tool for simulating physically-realistic earthquakes – to determine the stresses produced in the earth next to active faults. These simulations are paired with separate simulations of the granular material inside a fault zone where that granular material is subjected to dynamic stress perturbations similar to what is produced by the dynamic rupture simulations. Together, these two methods provide a unique window into earthquake triggering. For the first time we observe off-fault values, particularly stress and strain rate changes, produced by a passing fault rupture. The dynamic stress perturbations consist of sudden stress peaks coincident with rupture passage, often several MPa worth of change, far above what has been seen to cause triggering. When a similar perturbation was put into the granular code as a sudden pulse in the normal stress, several different behaviors were observed depending on the perturbation amplitude and the distance from failure. The work presented in this dissertation should be seen as the groundwork for a future linking of the dynamic rupture and granular codes into a single model that uses the output of one code as the inputs for another.
Payne, Ryan Matthew (2017). Integrating Grain-Scale and Fault-Scale Geomechanical Models: A Multi-Scale Study of Fault Triggering. Doctoral dissertation, Texas A & M University. Available electronically from