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| Titel |
Response of the San Jacinto Fault Zone to static stress changes from the 1992 Landers earthquake |
| VerfasserIn |
Mairead Nic Bhloscaidh, John McCloskey, Chris Bean |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250097501
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| Publikation (Nr.) |
 EGU/EGU2014-13093.pdf |
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| Zusammenfassung |
| Transfer of static stress has been proposed as a mechanism for interaction of earthquakes, by
Coulomb stress triggering. The ability of this model retrospectively to explain the qualitative
spatial characteristics of many aftershock distributions suggests that it has the potential to
become an important tool not only in short-term aftershock forecasting, but also in longer
term regional seismicity forecasts. The model also has implications for hazard assessment in
the context of induced seimicity. However, in practice, its suitability as part of any
prospective forecast will rely on determining a quantitative relationship between static stress
changes and aftershock probability. In order to make progress in validating such a
relationship, we perform an analysis of the seismicity response of the San Jacinto Fault Zone
to static Coulomb stress changes from the 1992 Landers earthquake sequence. Results show
that, in general, stress changes forecast rate changes well: we find a statistically
significant positive correlation between the change in rate and the magnitude of the
Coulomb stress change, with a correlation coefficient of 0.76 (equivalent to 5.6Ïă,
when compared to a Ï = 0 null hypothesis). This result is an important step in the
validation of Coulomb stress based methods for quantitative seismicity forecasting.
Comparison of the data with the predictions of the Coulomb rate-and-state model, yield
parameter estimates of AÏă = 0.4 bars and ta ~ 8 years. These estimates are likely to
be sensitive to the choice of reference seismicity model. With regard to the input
parameters of the Coulomb stress model, we find that, although there seems to be
a trade-off between the orientation and effective co-efficient of friction μ′ of the
target faults, in general structually constrained target fault orientations and values of
μ′ = 0.4 to 0.8 explain the data best, particularly for longer term aftershock rates. We
conclude that the correspondence between the predictions of Coulomb stress models
for aftershock seismicity and observed rate changes may be sensitive to strong
heterogeneity in aftershock locations and orientations associated with the presence of
large-scale structure in aftershock study areas. In these cases, we suggest that, where
the regional structure is mapped, incorporating it explicitly into Coulomb stress
models may improve the performance of quantitative Coulomb stress based forecasts. |
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