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(NAS Colloquium) Earthquake Prediction The Scientific Challenge (1996) / Chapter Skim
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Slip complexity in dynamic models of earthquake faults
Pages 3825-3829

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
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From page 3825...
... While automata facilitate rapid numerical computation, continuum models have the advantage of allowing more direct associations to be made between model parameters characteristic length and time scales, elastic constants and the like and observations of real seismic phenomena. Unlike the situation in fluid dynamics where the NavierStokes equation provides an agreed-upon description of the underlying physics, there is still no general consensus about what is the right model or equation for describing the motions of earthquake faults.
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From page 3826...
... The period of simple harmonic motion associated with this term is proportional to the time required for an elastic wave to traverse the crust depth, which is the same as the characteristic duration of slip at a single point on the fault in a very large, characteristic event. For real faults, this period is the order of seconds, the wave speed is the order of 10 kilometers/sec, and the corresponding length scale is the order of 10 kilometers.
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From page 3827...
... Complex, earthquake-like dynamics persists in this limit, and the frequency-magnitude distribution remains invariant throughout both the GR region and the region of large delocalized events. We also have looked analytically at propagating pulses in the model with viscosity and have examined the crossover from control by the grid size to control by the viscous length as the grid size becomes small (113.
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From page 3828...
... In our opinion, the principal outstanding uncertainty about these models is not the - U term or even the friction law but instead the extent to which the underlying origin of the complex behavior of real faults is captured by instabilities associated with inertial dynamics. An alternative hypothesis is that slip complexity in the real world is primarily the result of some quenched inhomogeneity associated with the complex geometry of real faults, and that inertial dynamics is of no more than secondary importance.
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From page 3829...
... On the other hand, if intrinsically smooth faults are deterministically chaotic systems that generate their own irregularities during unstable slipping motions, then models of the sort that we have described here will be essential for progress in earthquake prediction. The work of J.M.C.
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Key Terms

  • real faults
  • inertial dynamics
  • localized events
  • delocalized events
  • earthquake faults

  • crust depth
  • slipping threshold
  • friction law
  • imposed heterogeneities
  • friction laws

  • loading rate
  • fault surface
  • characteristic events
  • initial stress
  • stress drop

  • elastic waves
  • dispersion relation
  • externally imposed
  • individual events
  • continuum models

  • slipping events
  • wave speed
  • grid size
  • completely uniform
  • time scale

  • complex geometry
  • models exhibit
  • fault models
  • slipping speeds
  • complex patterns


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