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Roten, D. 1 , Olsen, K.B. 2 , Day, S.M. 2 , Dalguer, L.A. 1 and Fäh, D. 1

Large-scale 3-D Simulations of Spontaneous Rupture and Wave Propagation in Complex, Nonlinear Media. Roten, D. 1 , Olsen, K.B. 2 , Day, S.M. 2 , Dalguer, L.A. 1 and Fäh, D. 1. 1 Swiss Seismological Service / ETH Zürich 2 San Diego State University.

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Roten, D. 1 , Olsen, K.B. 2 , Day, S.M. 2 , Dalguer, L.A. 1 and Fäh, D. 1

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  1. Large-scale 3-D Simulations of Spontaneous Rupture and Wave Propagation in Complex, Nonlinear Media Roten, D.1, Olsen, K.B.2, Day, S.M.2, Dalguer, L.A.1 and Fäh, D.1 1 Swiss Seismological Service / ETH Zürich 2 San Diego State University Annual Meeting of the Seismological Society of America 17-19 April, Salt Lake City, UT

  2. Introduction • Advances in computer codes and increases in computational resources enable numerical prediction of ground motions at increasingly higher frequencies, e.g.: • M8 up to 2 Hz (Cui et al., 2010) • Chino Hills EQ up to 5 Hz • Nonlinear behavior of soft soils should be taken into account when predicting ground motions at frequencies above ~1 Hz • Nonlinear material behavior may also occur in the damage zone around the fault (on- and off-fault plasticity; e.g. Andrews (2005), Ma (2008). Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT 2

  3. Implementation of damage rheology in AWP-ODC Non-associative Drucker-Prager plasticity with yielding in shear (based on guidelines from SCEC/USGS Spontaneous Rupture Code Verification Project): Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT

  4. Implementation of damage rheology in AWP-ODC Return map algorithm: Time-dependent relaxation (Andrews, 2005): Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT

  5. Computational aspects • Staggering of grid requires interpolation of missing elements in stress tensor and initial stresses from adjacent nodes • Optimization that reduces number of interpolations results in significantly reduced computational cost Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT

  6. Verification against SCEC/USGS TPV13 • Spontaneous rupture on a planar, dipping fault (approximated by vertical fault in AWP-ODC) c = 5 Mpa tan(φ) = 0.85 Tv = 0 s Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT

  7. Convergence test (vertical strike-slip fault) Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT

  8. ShakeOut Earthquake Scenario • Based on kinematic source description (Graves et al., 2008) • visco-elastic medium Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT

  9. ShakeOut Earthquake Scenario with Plasticity Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT

  10. Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT

  11. ShakeOut Earthquake Scenario with Plasticity Visco-elastic Visco-elasto-plastic Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT 11

  12. ShakeOut Earthquake Scenario with Plasticity Final Principal Plastic Strain η at surface Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT

  13. ShakeOut Earthquake Scenario with Plasticity Final Principal Plastic Strain η atz = 600 m Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT

  14. Conclusions • We have implemented damage rheology based on the Drucker-Prager yield condition into the highly scalable 3D finite difference code AWP-ODC • The method has been validated against four finite element codes in the framework of the SCEC/USGS Spontaneous Rupture Code Verification Project • Computational cost of modeling plasticity amounts to an additional ~60% of the CPU time required for an elastic simulation • We simulate the ShakeOut-K earthquake scenario for a visco-elasto-plastic material, assuming that cohesions range from ~50 kPa in low-velocity sediments near the surface to several MPa at depth • Our results suggest that long-period (< 2 s) ground motion in the Los Angles area, amplified by a wave guide of interconnected sedimentary basins, could be significantly reduced as compared to visco-elastic solutions • Improved calibration of additional parameters (cohesion C and friction angle ϕ is required to reliably predict off-fault plasticity and nonlinear behavior of near-surface deposits Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT

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