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| Titel |
Early aftershock statistics |
| VerfasserIn |
C. Narteau, P. Shebalin, M. Holschneider, D. Schorlemmer |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024711
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| Zusammenfassung |
| In the Limited Power Law model (LPL) we consider that after a triggering event –Â the
so-called mainshock – rocks subject to sufficiently large differential stress can fail
spontaneously by static fatigue. Then, earlier aftershocks occur in zones of highest stress and
the c-value, i.e. the delay before the onset of the power-law aftershock decay rate, depends on
the amplitude of the stress perturbation in the aftershock zone. If we assume that this
stress perturbation is proportional to the absolute level of stress in the area, the
model also predicts that shorter delay occur in zones of higher stress. Here, we
present two analyses that support such a prediction. In these analyses, we use only
aftershocks of 2.5 < M < 4.5 earthquakes to avoid well-known artifacts resulting from
overlapping records. First, we analyze the c-value across different types of faulting in
southern California to compare with the differential shear stress predicted by a
Mohr-Coulomb failure criterion. As expected, we find that the c-value is on average
shorter for thrust earthquakes (high stress) than for normal ones (low stress), taking
intermediate values for strike-slip earthquakes (intermediate stress). Second, we test
the hypothesis that large earthquakes occur in zones where the level of stress is
abnormally high. Instead of the c-value we use the < t >-value, the geometric average of
early aftershock times. One more time, we observed that M > 5 earthquakes occur
where and when the < t >-value is small. This effect is even stronger for M > 6
earthquakes. |
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