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
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
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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
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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
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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
Material model
CPU time per iteration
Normalized CPU time
Elastic
0.18 s
100%
Elastoplastic
0.68 s
378%
Elastoplastic optimized
0.29 s
161%
Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT
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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
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Convergence test (vertical strike-slip fault)
Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT
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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
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ShakeOut Earthquake Scenario with Plasticity
Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT
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QuickTime™ and a
Motion JPEG OpenDML decompressor
are needed to see this picture.
Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT
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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
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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
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ShakeOut Earthquake Scenario with Plasticity
Final Principal Plastic Strain η at z = 600 m
Annual Meeting of the Seismological Society of America, April 17-19 2013, Salt Lake City, UT
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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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