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| Titel |
Systematic Changes Of Earthquake Rupture With Depth: A Case Study From The 2010 Mw 8.8 Maule, Chile, Earthquake Aftershock Sequence |
| VerfasserIn |
Ali Tolga Şen, Simone Cesca, Sebastian Heimann, Dietrich Lange, Torsten Dahm, Frederik Tilmann |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250105716
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| Publikation (Nr.) |
 EGU/EGU2015-5259.pdf |
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| Zusammenfassung |
| The very shallow part of subduction megathrusts occasionally hosts tsunami earthquakes,
with unusually slow rupture propagation. The aftershock sequence of the 2010 MW8.8 Maule
earthquake, offshore Chile, provides us with the opportunity to study systematic changes in
source properties for smaller earthquakes within a single segment of a subduction zone. We
invert amplitude spectra for double couple moment tensors and centroid depths of 71
aftershocks of the Maule earthquake down to magnitudes MW 4.0 and 6.8. In addition, we
also derive average source durations. Depending on the availability of data from a 130
broadband station temporary array, we employ two modelling schemes optimised
for regional and teleseismic data. The resulting focal mechanisms highlight the
correlation of the fault planes thrust earthquakes with the 3D slab model geometry
in the area, and the occurrence of normal faulting earthquakes on a crustal fault
system in the northernmost part of the study area. We find that shallower earthquakes
tend to have longer normalized source durations on average, similar to the pattern
observed previously for larger magnitude events. The normalised source durations of
normal faulting earthquakes are at the lower end of those for thrust earthquakes,
probably because of the higher stress drops of intraplate earthquakes compared to
interplate earthquakes. Notably, a similar depth dependence is observable for thrust
and normal earthquakes. We tentatively conclude from the similarity of the depth
dependence of normal and thrust events and between smaller and larger magnitude
earthquakes that the depth-dependent variation of rigidity is primarily responsible for the
observed pattern rather than frictional conditional stability at the plate interface
Tsunami earthquakes probably require both low rigidity and conditionally stable
frictional conditions; the presence of long duration moderate magnitude events is
therefore a helpful but not sufficient indicator for areas at risk of tsunami earthquakes. |
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