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http://hdl.handle.net/2122/6704

Authors:  Akinci, A.^{*} Perkins, D.^{*} Lombardi, A. M.^{*} Basili, R.^{*} 
Title:  Uncertainties in probability of occurrence of strong earthquakes for fault sources in the Central Apennines, Italy 
Title of journal:  Journal of Seismology 
Series/Report no.:  1/14(2010) 
Publisher:  Springer 
Issue Date:  Jan2010 
DOI:  10.1007/s109500089142y 
Keywords:  PROBABILITY OF OCCURENCES TIMEDEPENDENT 
Abstract:  Using the characteristic earthquake
model, we calculate the probability of occurrence
of earthquakes Mw > 5.5 for individual fault
sources in the Central Apennines for the 30year
period (2007–2037). We show the effect of timedependent
and timeindependent occurrence
(Brownian passage time (BPT) and Poisson) models
together with uncertain slip rates and uncertain
maximum magnitudes and, hence, uncertain
recurrence times. In order to reduce the large
prior geological slip rate uncertainty distribution
for most faults, we obtain a posterior slip rate
uncertainty distribution using a likelihood function
obtained from regional historical seismicity.
We assess the uncertainty of maximum magnitude
by assuming that the uncertainty in fault width
and length are described by a normal distribution
with standard deviation equal to ±20% of the
mean values. We then estimate the uncertainties
of the 30year probability of occurrence of a characteristic event using a Monte Carlo procedure.
Uncertainty on each parameter is represented
by the 16th and the 84th percentiles of
simulated values. These percentiles bound the
range that has a 68% probability of including the
real value of the parameter. We do these both for
the Poisson case and for the BPT case by varying
the aperiodicity parameter (α value) using the
values 0.3, 0.5, and 0.7. The Bayesian posterior
slip rate uncertainties typically differ by a factor
of about 2 from the 16th to the 84th percentile.
Occurrence probabilities for the next 30 years at
the 84th percentile typically range from 1% to
2% for faults where the Poisson model dominates
and from 2% to 21% where one of the BPT
models dominates. The uncertainty in occurrence
probability under the timedependent hypothesis
is very large, when measured by the ratio of the
84th to the 16th percentile, frequently being as
much as two orders of magnitude. On the other
hand, when measured by standard deviation,
these standard deviations range from 2% to 6%
for those faults whose elapsed time since previous
event is large, but always 2% or less for faults with
relatively recent previous occurrence, because the
probability of occurrence is always small. 
Appears in Collections:  04.06.99. General or miscellaneous Papers Published / Papers in press

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