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Group 1 – CSEP | Poster Abstracts
of giant earthquakes. However, there is a growing set of high-quality broadband teleseismic
recordings of large and giant earthquakes. In this poster, we use recordings from the 2003 Tokachioki
(Mw 8.3) earthquake as empirical Green’s functions to simulate the rock and soil ground
motions from the scenario M w 9.2 subduction earthquake expected on Cascadia subduction zone
in the frequency band of interest to flexible and large-scale buildings (0.1 to 1 Hz). The effect of
amplification by the Seattle basin is considered as a Green function which is derived from
deconvolving the teleseismic waves recorded at rock sites from soil sites at SHIP02 experiment.
These strong ground motions are used to simulate the fully nonlinear seismic responses of 20-story
and 6-story steel moment-frame buildings designed according to both the U.S. 1994 UBC and also
Japanese building code published in 1987. We consider several realizations of the hypothetical
subduction earthquake; the down-dip limit of rupture is of paticular importance to the simulated
ground motions in Seattle. If slip is assumed to be limited to offshore regions, then the building
simulations indicate that the building responses are mostly in the linear rang. However, our
simulation shows that buildings with brittle welds would collapse for rupture models where
rupture extends beneath the Olympic Mountains.. The ground motions have very long durations
(more than 4 minutes), and our building simulations should be considered as a minimum estimate
since we have used a very simple model of degradation of the structure.
1-068
DYNAMIC RUPTURE THROUGH A BRANCHED FAULT CONFIGURATION WITH
OFF-FAULT INELASTIC RESPONSE Templeton EL, Bhat HS, Dmowska R, and Rice JR
We analyze the propagation of shear cracks along branched fault paths with off-fault elastic-plastic
deformation. Numerical and experimental investigations have focused on both the role of off-fault
material behavior and that of geometrical complexities during earthquake rupture. Recent studies
of earthquake dynamics have allowed for off-fault inelastic deformation [Andrews, 2005,2007; Shi
and Ben-Zion, 2006; Templeton and Rice, 2008; Viesca et al., 2008; Duan, 2008]. These studies use
pressure-dependent yield criteria such as Mohr-Coulomb or Drucker-Prager (DP), which are
simple models for describing the onset of plastic deformation in granular or cracked materials. We
use the dynamic finite element method to extend previous branching studies to include effects of
inelastic off-fault response during dynamic slip-weakening earthquake rupture with an elastic DP
plastic off-fault material description.
We outline current understanding of the dynamics of rupture along branched fault systems, as
supported by field and laboratory comparisons with modeling, and then address rupture through
faults bordered by damage zones which have inelastic response during dynamic rupture. Previous
numerical studies by others in our group [Poliakov et al., 2002; Kame et al., 2003; Bhat et al.,
2004,2007; Fliss et al., 2005] based on boundary integral equation implementations of slipweakening
rupture showed how the choice of rupture path at a branching junction is determined
by the orientation of maximum compressive stress, branch angle, and rupture velocity at the
junction. We show how off-fault inelastic deformation contributes to the dynamic path selection
process.
In particular, we address the possibility of rupture through a fault branch along the Solitario
Canyon Fault (SCF) bordering Yucca Mountain. An issue is whether the next seismic rupture along
SCF could also induce rupture along a nearby fault such as the Windy Wash Fault or the
Boomerang Fault. Analyses using branch configurations suggested by cross-sectional views
[Brocher et al., 2998; Potter et al., 1999,2004] with a vertical tectonic pre-stress suggest that
branching is unlikely for these configurations when inelastic deformation is allowed in the bulk
except in cases of extreme stress drops or super shear rupture velocities. We also address the
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