ISSN:
1420-9136
Keywords:
Friction
;
Earthquake mechanics
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract A review of simple models and observations suggests that the main first-order features of active faulting-mechanical instability, the frequency-magnitude relations, seismic and aseismie slip, seismic radiation, incoherency and rupture stoppage — may be explained by a single characteristic of crustal faults: the spatial variation of the effective frictional stress, which resists slippage on faults. Faultoffset data suggest that rupture propagation ceases in regions of high resistance which act, as barriers. In these regions slippage is associated with negative stress drop. The spacing λ and the amplitudeA(λ) of the barriers, as inferred from the frequency-magnitude and moment relation for earthquakes, obeys a simple statistical relationA(λ)∼λp. On the scale of particle motion, this variability of frictional stress provides a mechanical instability which may be associated with the concept of dynamic friction. Invariably, the rapid particle motion in the model is always preceded by accelerated creep. The particle acceleration is highly irregular, giving rise to an almost random acceleration record on the fault. The particle displacement is relatively smooth, giving rise to simple displacement time function in the far field. Rupture propagation time is approximately proportional to the gradient of frictional stress along the fault. Consequently sharp changes of this stress may cause multiple events and other long period irregularities in the fault motion. The power density spectrum associated with the frictional stress implies that stress may be related to a Poisson distribution of lengths. The autocorrelation of such type of distribution yields a correlation lengthk L −1 , similar perhaps toHaskell's (1964) andAki's (1967) correlation lengths inferred from spectral analysis of seismic waves. The partial incoherency of faulting implies that preseismic deformation may be significantly incoherent, consequently the prediction of small moderate earthquakes may be subject to inherent uncertainties. We conclude that frictional stress heterogeneities may be necessary and sufficient to explain active faulting associated with small and moderate earthquakes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00876550
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