Jim Dieterich Keith RichardsDinger UC Riverside Funding USGS NEHRP SCEC Representation of Fault Friction Constitutive relation State evolution Stress evolution Terms in red are additional ones due to normal stress variations Linker and Dieterich 1992 ID: 273069
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Slide1
RSQSim
Jim Dieterich
Keith Richards-Dinger
UC Riverside
Funding:
USGS NEHRP
SCECSlide2
Representation of Fault Friction
Constitutive relation:
State evolution:
Stress evolution:
Terms in red are additional ones due to normal stress variations (Linker and Dieterich, 1992)
Interaction coefficients,
K
, calculated from the dislocation solutions of Okada, 1992
Tectonic stressing rates derived from backslipping the model
Numerical integration too slow for the scale of problems we would like to address Slide3
Representation of Fault Friction
Constitutive relation:
State evolution:
Stress evolution:
State 1: nucleation
State 0: locked fault
State 2: seismic slip Slide4
Representation of Fault Friction
No predetermined failure stress or stress drop
Stress drop scales roughly as Slide5
Representation of Fault Friction
No predetermined failure stress or stress drop
Stress drop scales roughly as Slide6
Approximations to
Elastodynamics
Parameters that influence the rupture process:
Slip speed during coseismic slip determined from shear impedance considerationsReduction of a
on patches nearby to seismically slipping patchesStress overshoot during rupturesSlide7
Effect of Overshoot on Rupture Characteristics
Large overshoot (13%)
Small overshoot (1%)Slide8
Approximations to
Elastodynamics
Values for rupture parameters determined by comparison with fully dynamic rupture models
DYNA3D –
Fully
dynamic finite element simulation
RSQsim – Fast simulation
Propagation time 14.0
s
Propagation time 14.3 sSlide9
Representation of
Viscoelasticity
afterslip
Rate-strengthening (a > b) patches
Approximated as always sliding at steady-stateDistributed asDeep creeping extensions to major faultsShallow creep on major faultsEntire creeping sections (e.g. SAF north of Parkfield)
Possibly with small imbedded stick-slip patchesMore complicated mixed stick-slip and creeping areas (e.g. Hayward Fault) Slide10
Representation of
Viscoelasticity
afterslip
Penetration of slip of large events into creeping zoneSlide11
Representation of
Viscoelasticity
afterslip
Fraction of moment release in creeping section
AftershocksSlide12
Representation of
Viscoelasticity
afterslip
1989 Loma
Prieta
Earthquake
Simulation
Small repeating earthquakesSlide13
Power-law temporal clustering
Decay of aftershocks follows Omori power law
t
-p with
p = 0.77Foreshocks (not shown) follow an inverse Omori decay with
p
= 0.92
Dieterich and Richards-Dinger, PAGEOPH, 2010
Stacked rate of seismicity relative to mainshock origin timeSlide14
Power-law temporal clustering
Interevent
Waiting Time Distributions
California Catalog 1911 – 2010.5Slide15
Power-law temporal clustering
Space – Time DistributionsSlide16
Earthquake cluster along San Andreas Fault
M7.3
43 aftershocks in 18.2days
All-Cal model – SCEC Simulator Comparison ProjectSlide17
Earthquake cluster along San Andreas Fault
M6.9
Followed by 6 aftershocks in 4.8 minutes
All-Cal model – SCEC Simulator Comparison ProjectSlide18
Earthquake cluster along San Andreas Fault
M7.2
All-Cal model – SCEC Simulator Comparison ProjectSlide19
slip ~2.3 - 4.0 cm
duration ~10-40 days
inter-event time - ~10-19 months
simultaneous slip in different
areas
no Omori clustering
spontaneous segmentation
Colella et al.,
submitted
Slow-slip eventsSlide20
Summary or Conclusions (if appropriate or desired)