Measuring the onset of locking in the Peru-Chile trench with GPS and acoustic measurements

The subduction zone off the west coast of South America marks the convergence of the oceanic Nazca plate and the continental South America plate. Nazca-South America convergence over the past 23 million years has created the 6-km-deep Peru-Chile trench, 150 km offshore. High pressure between the pla...

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Bibliographic Details
Published in:Nature 2005-03, Vol.434 (7030), p.205-208
Main Authors: Norabuena, Edmundo, Gagnon, Katie, Chadwell, C. David
Format: Article
Language:English
Subjects:
Applied geophysics
Deformation
Earth sciences
Earth, ocean, space
Earthquakes
Earthquakes, seismology
Exact sciences and technology
Geology
Global positioning systems
GPS
High pressure
Humanities and Social Sciences
Internal geophysics
letter
Marine
multidisciplinary
Ocean floor
Plate tectonics
Science
Science (multidisciplinary)
Seismic activity
Seismology
Tectonics. Structural geology. Plate tectonics
Tidal waves
Transponders
Tsunamis
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Summary:The subduction zone off the west coast of South America marks the convergence of the oceanic Nazca plate and the continental South America plate. Nazca-South America convergence over the past 23 million years has created the 6-km-deep Peru-Chile trench, 150 km offshore. High pressure between the plates creates a locked zone, leading to deformation of the overriding plate. The surface area of this locked zone is thought to control the magnitude of co-seismic release and is limited by pressure, temperature, sediment type and fluid content. Here we present seafloor deformation data from the submerged South America plate obtained from a combination of Global Positioning System (GPS) receivers and acoustic transponders. We estimate that the measured horizontal surface motion perpendicular to the trench is consistent with a model having no slip along the thrust fault between 2 and 40 km depth. A tsunami in 1996, 200 km north of our site, was interpreted as being the result of an anomalously shallow interplate earthquake. Seismic coupling at shallow depths, such as we observe, may explain why co-seismic events in the Peruvian subduction zone create large tsunamis.
ISSN:0028-0836
1476-4687
DOI:10.1038/nature03412