Space-time analysis of observed and modeled aftershock sequences
Palaeontology
Final Report Abstract
We analyzed aftershock sequences from Landers (1992), Northridge (1994), and L’Aquila (2009). For Landers, we showed that the p-value varies along strike and presented a model whereby these variations are controlled by the strike of the fault relative to the regional stress field. Regions where the fault strike is optimally oriented for fluid flow (e.g. low effective normal stress) result in lower p-values relative to regions where high-effective normal stress limit flow from depth. Modeling of the Northridge aftershocks showed a very good comparison between aftershock hypocenters and the fluid pressure evolved from the co-seismic release of trapped highpressure fluid source. Inversion of focal mechanisms from the L’Aquila aftershocks demonstrated high pressure fluids at depth that likely drove this sequence. Thus, we showed evidence for fluid-driven aftershocks in strike-slip (Landers), thrust (Northridge), and normal faulting (L’Aquila) environments. Investigations are underway to further demonstrate a fluid-driven component that is currently not widely accepted in the community. We also developed a poro-elastic plastic numerical model designed to run exclusively on the GPU platform, which both significantly improves on numerical resolution while simultaneously reduces simulation run times. This model has potential to significantly improve on existing Thermal-Hydraulic-Mechanical-Chemical (THMC) simulators, with application to earthquake physics, enhanced geothermal systems, carbon sequestration, and other systems dominated by fluid-rock interactions.
Publications
- (2012). Modeling the spatio-temporal evolution of fracture networks and fluid-rock interactions in GPU: Applications to lithospheric geodynamics (Doctoral dissertation, Bonn)
Galvan, B.
- (2008), Note on rain-triggered earthquakes and their dependence on karst geology, Geophysical Journal International, 173(1), 334-338
Miller, S. A.
(See online at https://doi.org/10.1111/j.1365-246X.2008.03735.x) - (2010), High pressure fluid at hypo-central depths in the L'Aquila region inferred inferred from earthquake focal mechanisms, Geology, 38, pp. 995-998
Terakawa, T., A. Zoporowski, B. Galvan, and S. A. Miller
- (2013), A full GPU simulation of evolving fracture networks in a heterogeneous poro-elasto-plastic medium with effective-stressdependent permeability, in: GPU Solutions to Multi-scale Problems in Science and Engineering, edited, pp. 305-319, Springer
Galvan, B., and S. A. Miller
