Interactions and triggering in a 3-D rate-and-state asperity model
Résumé
We present a 3-D continuous quasi-dynamic rate-and-state model of multiple
seismic asperities forced by surrounding aseismic creep and motivated by observations of
coplanar multiplets. Our model allows to study the physics of interactions among a set of
asperities. First, we show that the amount of interactions and clustering, characterized by
the Omori law and interevent time distribution, depends on how far the system is from a
critical density of asperities, which is related to the friction properties of the barriers
separating the sources. This threshold controls the ability of a population of asperities to
destabilize the creeping barriers between them and therefore determines whether dynamic
sequences including several asperities in the same event might occur, in agreement with
what is expected from observed magnitude-frequency distributions. Therefore, the
concept of critical density of asperity provides a mechanical interpretation of statistical
properties of seismicity. As an illustration, we used our numerical results in the specific
case of Parkfield in the period preceding the Mw 6, 2004 earthquake, in order to infer the
steady state friction parameter (a–b) characterizing the creep of this part of the San
Andreas Fault. We estimate a value of (a-b) that locally exceeds 0.001, which is in the
upper range of what has already been proposed for the postseimic period of the
Mw 6,2004 Parkfield earthquake.
Domaines
Géophysique [physics.geo-ph]Origine | Fichiers éditeurs autorisés sur une archive ouverte |
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