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| Titel |
Earthquake nucleation scaling from laboratory to Earth |
| VerfasserIn |
Stefan Nielsen, Yoshihiro Kaneko, Chris Harbord, Soumaya Latour, Brett Carpenter, Nicola de Paola |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250153826
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| Publikation (Nr.) |
 EGU/EGU2017-18853.pdf |
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| Zusammenfassung |
| Migrating foreshock sequences along major plate boundaries and geodetic transient
anomalies have been interpreted as indicators of aseismic creep for days to months prior to
the initiation of earthquakes. In other cases no significant precursory activity is detected, even
at well-instrumented sites, suggesting an abrupt rupture initiation. Both the nucleation
size (e.g. Rice and Ruina’s hRR∗ or Andrew’s Lc) or its duration can be highly
variable. Here we analyse the scaling of nucleation and the controls on stick-slip
instability based on a review of recent laboratory experimental results. (1) Rupture
propagation experiments on smooth model faults show a two-phase nucleation
process with variable size and duration depending on loading rate, normal stress
and frictional parameters. These results can be reproduced by numerical models
incorporating rate-and-state friction laws, and can be up-scaled to simulate the nucleation
process of crustal earthquakes. We used frictional properties from samples of the San
Andreas Fault Observatory at Depth (SAFOD) to model the nucleation phase for
magnitude∼2 repeating earthquakes at a 2.8-km depth. We predict that the nucleation could
be detectable a few hours before the earthquake by strain measurements in the
existing borehole. (2) An alternative set of experiments on rough model faults,
instead, shows that initiation of rupture is primarily controlled by the size and the
amount of heterogeneity induced by the fault topography and its interplay with the
normal stress. In this case the onset of stick-slip is not predicted by the stability
analysis within the rate-and-state framework, but rather by energy considerations
more akin to Griffith’s criterion in the presence of flaws. Although these two sets of
experimental observations and their modelling are difficult to reconcile, they may be
representative end members of earthquake faults with different degrees of heterogeneity. |
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