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| Titel |
Active deformation processes across a megathrust-segment boundary, south-central Chile |
| VerfasserIn |
M. S. Moreno, J. Klotz, D. Melnick, J. Bolte, H. Echtler, K. Bataille |
| 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 |
250028525
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| Zusammenfassung |
| The south-central Chile margin is an active plate boundary where a variety of tectonic
processes, including postseismic mantle relaxation, interseismic strain accumulation, sliver
motions and crustal faulting are documented. GPS data and finite-element models with
complex geometries are presented to gain insight into the active deformation in the
vicinity of two megathrust-earthquake segments: the Valdivia and Concepción rupture
zones. GPS vectors are heterogeneously distributed in two domains that follow
the megathrust segments. Models which simulate only interseismic locking on the
plate interface and postseismic relaxation after an uniform coseismic slip during
the 1960 Valdivia earthquake (Mw=9.5) not fully reproduce the observed surface
deformation. In order to distinguish between the main processes producing the
regional-scale heterogeneity of surface velocities, we model: (1) the postseismic
viscoelastic deformation induced by a non-uniform coseismic slip distribution, (2)
the interseismic kinematic coupling, and (3) the interseismic effect of a crustal
fault rooted in the plate interface. We find that interseismic locked asperities are
spatially coincident with the historic earthquake rupture zones, which are separated
by a sharp boundary of low (~ 50%) kinematic coupling. A regional pattern of
clockwise rotations arise from postseismic mantle rebound at the overlap area of
the rupture zones and extend over a broad segment between the forearc and the
back-arc. Locally, counterclockwise block rotation is observed in a limited area
south of the Lanalhue fault, and may be related to transpression at the northern
leading edge of a forearc sliver. In the Concepción domain, models that include a
dextral-reverse crustal fault better reproduce the GPS observations. Our study suggests
that upper-plate crustal faults in addition to earthquake-cycle transients exert an
important control on deformation processes at megathrust-segment boundaries. |
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