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ensure accuracy. Aftershocks are an extreme example of short-
term earthquake clustering that appears to be quite distinct
from the long-term regional clustering of large earthquakes
discussed above. Aftershocks can temporarily increase the local
seismicity rates to more than 10,000 times the pre-mainshock
level. Although Coulomb stress interactions provide an
explanation for many aftershock patterns, those models alone do
not account for either the rates of seismicity that occur in
response to the stress changes or the subsequent decay of rates
inversely proportional to time, as expressed in Omori’s
aftershock decay law (Equation 2.8). The most fully developed
explanation for these and other properties of aftershocks is
based on the rate- and state-dependent fault frictional
properties observed in laboratory experiments (see Sect