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| Titel |
Seismic and aseismic slip on the central Peru megathrust |
| VerfasserIn |
Hugo PERFETTINI, Jean-Philippe Avouac, Hernando Tavera, Mohamed Chlieh, Jean-Mathieu Nocquet, Dominique Remy, Andrew Kositsky, Anthony Sladen |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053712
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| Zusammenfassung |
| In the last couple of decades, advances in the analysis techniques
and instrumentation have improved significantly our capability to
document the different stages of the seismic cycle, namely the co-,
post- and inter-seismic phases. To this respect, the Mw8.0 Pisco,
Peru, earthquake of August 2007 is exemplary, with numerous data
sets allowing exploring the details of each phase and studying their
relationship. The post-seismic deformation following the mainshock is
studied using a local network of continuous GPS stations together with
various InSAR interferograms. Inversion for slip on the fault is carried
on using the PCAIM inversion method
(http://www.tectonics.caltech.edu/resources/pcaim/). The inversion
shows two patches of significant afterslip located near the co-seismic
asperities, in agreement with the idea that coseismic slip triggers
afterslip. Aftershocks are located on top of the patches of high
postseismic slip, while they are anti-correlated with the position of the co-seismic asperities, consistent with the idea that afterslip drive
aftershocks. Post-seismic relaxation is consistent with rate and state
friction, assuming a rate strengthening rheology. The most prominent
of those post-seismic patches coincides with the subducting Nazca
ridge, an area also characterized by a locally low interseismic coupling
and which seems to have acted as a barrier to seismic rupture
propagation repeatedly in the past. The ’seismogenic’ portion of the
megathrust thus appears to be paved with interfingering of
rate-weakening and rate-strengthening patches. The
rate-strengthening patches are shown to contribute to an unsuspected
high proportion of aseismic slip and to determine the extent and
frequency of large interplate earthquakes. Aseismic slip accounts for
as much as 50-70% of the slip budget on the seismogenic portion of
the megathrust of central Peru and the return period of Mw 8.0
earthquakes in the Pisco area is estimated to 250 years, a value in
good agreement with the 261 years between the 2007 Pisco
earthquake and the previous large megathrust earthquake in this area
which occurred in 1746. |
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