Document Type

Article

Publication Date

12-12-2008

Publication Title

Geochemistry, Geophysics, Geosystems

Abstract

Motion on the Atacama Fault System (AFS) in northern Chile is driven by Andean subduction zone processes. We use two approaches, observational and theoretical, to evaluate how the AFS and other forearc faults responded to coseismic stress induced by one well-studied megathrust earthquake, the 1995 Mw = 8.1 Antofagasta event. We use synthetic aperture radar interferometry (InSAR) to search for small-scale coseismic and postseismic deformation on individual faults. The InSAR data are ambiguous: some images show offset consistent with coseismic faulting on the Paposo segment of the AFS and others lack such signal. The fact that we do not observe the fault-like displacement in all coseismic interferograms suggests that atmospheric contamination, not tectonic deformation, is responsible for the signal. To explore the capacity of the earthquake to trigger motion on upper plate faults, we use seven published slip maps constrained by geodetic and/or seismic data to calculate static and dynamic Coulomb stress change (CSC) on faults in the Antofagasta region. The static CSC field varies between models and depends on the distribution of coseismic interplate slip. On the basis of the CSC distribution predicted by our preferred model constrained by all available data, we suggest it was unlikely that the Antofagasta earthquake directly triggered normal motion on the AFS, and the InSAR data are consistent with this null result. Field reports of normal faulting related to the earthquake may reflect recent (but not coseismic) motion or highly localized behavior not representative of the regional coseismic stress field.

Volume

9

Issue

12

DOI

10.1029/2008GC002155

ISSN

1525-2027

Rights

Licensed to Smith College and distributed CC-BY under the Smith College Faculty Open Access Policy.

Included in

Geology Commons

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