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| Titel |
Slip distribution of the 1960 Chile earthquake using a FEM with precise geometry |
| VerfasserIn |
M. S. Moreno, J. Bolte, J. Klotz, D. Melnick, 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 |
250028407
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| Zusammenfassung |
| The 1960 Chile earthquake (Mw=9.5) is the largest recorded seismic event. It caused a
~950-km-long rupture between the subducting Nazca plate and the South American
continent. Ongoing postseismic mantle relaxation, interseismic strain accumulation, motion
of a forearc sliver, and block rotation controlled by crustal faults have been documented in the
vicinity of the earthquake rupture zone. A variable slip distribution for this event has been
made using a dislocation model with simple planar slab geometry (Barrientos and Ward,
1990), based on the inversion of sea-level changes and elevation differences. We use the same
155 vertical displacements of the land relative to sea-level (Plafker and Savage, 1970) to
determine the slip distribution of the source, applying a finite element model (FEM) with
precise geometry. The Green’s function matrix containing the kernel of the coseismic model
displacements is constructed. Classic Laplace constraints on the slip distribution can
not be applied due to the complexity of the geometry. Therefore, we implemented
isoparametric finite element constraints to smooth the slip of neighbor nodes on the
rupture. An optimization routine is used for matrix inversion with positive constraint
allowing only thrust slip. This improved FEM inversion method can handle very
complex nodes distributions, include viscosity effects and implement layering of
different material properties, providing a precise tool to estimate unknown fault
slip distribution. Our results are significantly smoother than the previous results
based on planar geometry. The obtained rupture zone (38-46Ë S) is restricted to the
continental shelf in contrast to Barrientos and Ward (1990) finding that extended to below
the volcanic arc. A ~300-km-long asperity with slip over 30 m is located at the
northern segment of the rupture near of Valdivia. The faulting area narrows southward,
showing two peaks of slip at 42Ë and 43Ë S. Our results give a geodetic moment of
~1Ã1023Nm, which corresponds to ~45% of the seismic moment, confirming a
moment deficit. The missing moment could reflect non-linear deformation near the
megathrust and/or different sensitivity of both seismic and geodetic methodologies. |
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