(NAS Colloquium) Earthquake Prediction The Scientific Challenge (1996) / Chapter Skim
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Rock friction and its implications for earthquake prediction examined via models of Parkfield earthquakes
Rock friction and its implications for earthquake prediction examined via models of Parkfield earthquakes
Pages 3803-3810
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From page 3803... ...
The magnitude of the strain rate at the earth's surface due to this accelerating slip seems lower than the detectability limit of instruments in the presence of earth noise. Although not specifically modeled, microseismicity related to the accelerating creep and to creep events in the model should be detectable.
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No laboratory experiments combine the large displacement, high slip rate, high normal stress, and presence of pressurized pore fluids that characterize dynamic earthquake slip. Most experiments involving high slip velocity (e.g., refs.
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This model takes the boundary conditions relevant to the Parkfield section of the San Andreas fault, and by using constitutive parameters consistent with laboratory experiments, generates a spontaneous sequence of characteristic earthquakes. The magnitude and spatial and temporal extent of any premonitory creep in this model can be studied to see whether it could be detected and form the basis for a prediction of the earthquake.
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3806 Colloquium Paper: Tullis Proc.
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The coarseness of the grid precludes explicit modeling of small earthquakes. It is reasonable to imagine that the more rapid the slip event, the more numerous the small earthquakes or the larger their size, since these more rapid creep events correspond to larger moment rates.
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Fig. 6 shows plots of the maximum strain rates observed on the Earth's surface in the model versus logarithm of time before the earthquake, together with an estimate of the detectability limit for sampling at appropriate rates for that period.
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They peak at various times corresponding to creep events that occur on only one cell. The moment rate for 30 1-km cells under Middle Mountain is also shown, as is the moment rate corresponding {v 1 and to 30 cells slipping at 35 mm/year.
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From page 3810... ...
The behavior of the model Parkfield earth quakes discussed here is based on laboratory determinations of rock friction constitutive laws. The model earthquakes show premonitory slip prior to the eventual mainshock, but the spatial and temporal extent of it is relatively small.
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