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| Titel |
Time behavior of aftershock series simulated by using a modified version of the Dynamic Fiber Bundle (FBM) model |
| VerfasserIn |
M. D. Martínez, M. Monterrubio, X. Lana |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066230
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| Zusammenfassung |
| The Fiber Bundle Model (FBM) has been frequently used to analyze the rupture process in
heterogeneous materials. The FBM is a simple discrete stochastic fracture model
suitable to either close analytical or fast numerical solutions. The dynamic version of
the FBM simulates the failure of materials due to different kind of phenomena
like static fatigue, delayed-rupture, stress-rupture or creep-rupture. Three basic
components are common to all FBM: a discrete set of N elements located at the sites of a
d-dimensional lattice; a probability distribution for the failure of individual elements,
where the most common is the Weibull distribution; and, a load-transfer rule which
determines how the load carried by a failed element is distributed among the surviving
elements. The time behavior of three series of aftershocks in Southern California,
associated with the main shocks of Landers (Mw = 7.3, 1992), Northridge (Mw = 6.7,
1994) and Hector Mine (Mw = 7.1, 1999) is simulated using a modified version of
the dynamic FBM. This version makes use of a property of the static FBM that
allows establishing a threshold value, Ïăth, for the stress that each elemental fiber
can hold without failure. Given that an aftershock sequence is a stress relaxation
process, a dissipative term is introduced. The local load sharing (LLS) is chosen as
load-transfer rule. The starting stress values for the set of fibers are assumed to
follow a uniform probability distribution. After the failure of an elemental fiber, the
load is transferred to the adjacent fibers, and the increase of stress can lead one or
more fibers to overcome a threshold stress Ïăth, generating an avalanche event.
The avalanche ends when all the surviving fibers have a stress value below Ïăth.
The avalanche-like events are related to local stress accumulations, which lead
to shorter inter-event times and a sudden stress release. These accelerations are
embedded in the general trend of stress relaxation, which is in agreement with the
time behavior observed in the three seismic aftershock sequences. The numerical
simulations are controlled by three parameters: the Weibull exponent, Ï, the dissipative
ratio, Ï, and the number of fibers, N. A large number of numerical simulations
have been carried out to find the set of parameters (Ï, Ï, N) best reproducing the
fundamental characteristics of the three empirical aftershock series, such as the
parameters of the modified Omori law and the time evolution of the generation
rate and the number of aftershocks within the episodes of sudden stress release. |
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