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Group A, Poster #207, SCEC Community Models (CXM)

New computational workflows to examine the role of 3D fault architecture on long-term slip rates and off-fault deformation: A case study from the Eastern California Shear Zone

George Pharris, John Naliboff, Veronica B. Prush, Timo Heister, Menno Fraters, & Frederick LaCombe
Poster Image: 

Poster Presentation

2023 SCEC Annual Meeting, Poster #207, SCEC Contribution #13187 VIEW PDF
Lithospheric deformation is accommodated through a combination of localized deformation along faults and distributed as off-fault deformation (OFD). The spatiotemporal partitioning of deformation in fault zones is a function of a wide range of physical parameters, including first-order lithospheric structure and the 3D architecture and rheology of faults through both the brittle and ductile regimes. Numerous computational investigations have provided significant insight into the relationship between these physical parameters and distinct styles of seismogenic behavior. However, the majority of these studies treat faults as 2D (planar) structures, neglecting the potential role of 3D fault str...ucture on deformation in the brittle regime and across the brittle-ductile transition.

We present new computational workflows for investigating the role of 3D fault architecture and lithospheric structure on long-term fault slip rates and partitioning between on- and off-fault deformation. Our investigation focuses on the Eastern California Shear Zone, where the SCEC Community Fault Model (CFM) and additional published map data are used to define the first-order fault network structure. A mesh-independent representation of 3D fault structure (width, dip, depth extent, rheology) is created using the Geodynamic World Builder (GWB) software package. The GWB representation of the fault architecture provides initial conditions for instantaneous, kinematically-driven forward simulations of deformation in the mantle convection and lithospheric dynamics code ASPECT, whose capabilities include adaptive mesh refinement (AMR), advanced linear and nonlinear solvers, and massive parallel scaling. We use these features to achieve geologically-feasible fault widths (<500 m) and to examine the role of both brittle and ductile fault rheology on long-term fault slip rates and OFD. Our preliminary results reveal changes in fault orientation and the distribution of faults within the broader fault network can produce complex along-strike variations in fault slip-rates. Varying the brittle and viscous strength of faults relative to off-fault regions produces additional significant variations in the magnitude of fault slip rates and deformation partitioning. Our presentation will expand on these preliminary findings and highlight potential extensions of our methodology to include additional physical complexity.