Annual Meeting - SCEC.org

Poster Abstracts
San Andreas fault system, and an earthquake early warning can be issued. We show results from the southern Californian
CRTN sites during the 2010 Mw 7.2 El Mayor-Cucapah earthquake. The data collected showed significant ground motions in
the Imperial Valley a few seconds after the initial earthquake and for a few minutes, the movement reverberated across all of
southern California (Bock et al., 2011). The SOPAC group is working on rapid determination of earthquake location,
magnitude and fault plane using the site displacements computed by the network adjustment (Crowell et al., 2009; Melgar et
al., 2011).
MECHANICS OF STRESS TRANSFER FROM PLATE MOTION TO PLATE BOUNDARY FAULTS: DYNAMIC
MODELS OF EARTHQUAKE CYCLES ON A STRIKE-SLIP FAULT (B-146)
C.S. Takeuchi and Y. Fialko
Existing models of interseismic deformation are predominantly kinematic: loading is applied by prescribing slip on
dislocations, either at a constant rate below the seismogenic layer (the Savage-Burford model) or quasi-periodically in the
seismogenic layer on top of a viscoelastic substrate (the Elsasser model). These loading mechanisms are not physically
consistent. In particular, kinematic viscoelastic cycle models produce absolute stresses on the seismogenic fault that are
opposite to the sense of tectonic loading. We consider dynamic (stress-controlled) models of strike-slip faults that are driven
by far-field tractions due to relative plate motion. We use antiplane strain finite element models to simulate quasi-periodic
earthquakes on a fault in a brittle crust underlain by a viscoelastic medium. Each model is driven by far-field plate motion at a
rate of 4 cm/yr, similar to the San Andreas Fault (SAF) in California. Slip occurs when the shear stress on the fault exceeds a
prescribed threshold. We analyze stresses, strain rates, and surface deformation for models assuming various rheologies of a
ductile substrate, including a) linear Maxwell rheology, b) power law temperature dependent rheology assuming a given
linear geotherm, and c) power law temperature dependent rheology with thermo-mechanical coupling. The latter class of
models gives rise to a permanent localized shear zone due to the interaction of viscous dissipation and heat conduction. An
initial temperature perturbation is generated via a kinematically-driven thermal “maturation” of the fault at a constant slip
rate over “geological” (millions of years) time scales. Strain localization in the power law viscoelastic medium due to thermomechanical
coupling is used as a proxy for all strain-weakening mechanisms (including e.g. grain-size reduction). Simulations
are performed for “dry” and “wet” rheological endmembers for the viscoelastic substrate. We compare the predicted surface
velocities and strain rates to available observations from the SAF. We find that a dry temperature-dependent power law
rheology best reproduces time-dependent surface deformation and generates reasonable deviatoric stresses in the crust and
upper mantle.
STATIC DISPLACEMENTS COMPUTED FROM SEISMIC WAVEFIELD SIMULATIONS: VALIDATION
TESTS FOR HOMOGENEOUS AND 1D STRUCTURE (A-061)
C. Tape, J.P. Loveless, and B.J. Meade
Earthquake 240 240 c 240 y 240 c 240 l 240 e 240 240 p 240 r 240 o 240 c 240 e 240 s 240 s 240 240 i 240 n 240
240 s 240 o 240 u 240 t 240 h 240 e 240 r 240 n 240 240 C 240 a 240 l 240 i 240 f 240 o 240 r 240 n 240 i 240 a 240 240 a 240 r 240 e 240
240 c 240 o 240 m 240 m 240 o 240 n 240 l 240 y 240 240 i 240 n 240 f 240 e 240 r 240 r 240 e 240 d 240 240 f 240 r 240 o 240 m 240
240 m 240 o 240 d 240 e 240 l 240 s 240 240 o 240 f 240 240 g 240 e 240 o 240 d 240 e 240 t 240 i 240 c 240 240 d 240 a 240 t 240 a 240
240 a 240 s 240 s 240 u 240 m 240 i 240 n 240 g 240 240 t 240 h 240 a 240 t 240 240 t 240 h 240 e 240 240 u 240 p 240 p 240 e 240 r 240
240c 240r 240u 240s 240t 240 240c 240a 240n240 240b 240e 240 240t 240r 240e240a 240t 240e 240d 240 240a 240s 240 240a 240
240s240i240m240p240l240e240 240h240o240m240o240g240e240n240e240o240u240s240 240e240l240a240s240t240i240c240
240h240a240l 240f 240s 240p 240a240c240e 240. 240 240H 240o 240w 240e 240v 240e240r 240,240 240i 240t240 240i240s 240
240 w 240 e 240 l 240 l 240 240 k 240 n 240 o 240w 240n 240 240 t 240 h 240 a 240 t 240 240 m 240 a 240 t 240 e 240 r 240 i 240a 240 l 240
240p240r240o240p240e240r240t240i240e240s240 240(240f240o240r240 240e240x240a240m240p240l240e240,240 240V240s240
240o240r240 240V240p240)240 240v240a240r240y240 240b240y240 240m240o240r240e240 240t240h240a240n240 240a240n240
240 o 240 r 240 d 240e 240 r 240 240 o 240 f 240 240 m 240 a 240 g 240n 240 i 240 t 240 u 240 d 240e 240 , 240 240 f 240 r 240 o 240 m 240
240 l 240 o 240 w 240 240 w 240 a 240 v 240 e 240 240 s 240 p 240 e 240 e 240 d 240 s 240 240 i 240 n 240
240u240n240c240o240n240s240o240l240i240d240a240t240e240d240 240s240e240d240i240m240e240n240t240s240 240t240o240
240 h 240 i 240 g 240 h 240 240 w 240 a 240 v 240 e 240 240 s 240 p 240 e 240 e 240 d 240 s 240 240 i 240 n 240 240 t 240 h 240 e 240
240u240p240p240e240r240m240o240s240t240 240m240a240n240t240l240e240 240b240e240l240o240w240 240t240h240e240
240 M 240o 240 h 240 o 240. 240 240T 240h 240i 240s 240 240 r 240 a 240 n 240g 240e 240 240 o 240 f 240 240 w 240a 240 v 240e 240
240 s 240 p 240 e 240 e 240 d 240 s 240 240 i 240 s 240 240 p 240 r 240 e 240 s 240 e 240 n 240 t 240 240 w 240 i 240 t 240 h 240 i 240 n 240
240c240r240u240s240t240a240l240 240m240o240d240e240l240s240 240i240n240 240s240o240u240t240h240e240r240n240
240 | Southern California Earthquake Center