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Published February 2017 | Supplemental Material + Published
Journal Article Open

From the seismic cycle to long-term deformation: linking seismic coupling and Quaternary coastal geomorphology along the Andean Megathrust

Abstract

Measurement of interseismic strain along subduction zones reveals the location of both locked asperities, which might rupture during Megathrust earthquakes, and creeping zones, which tend to arrest such seismic ruptures. The heterogeneous pattern of interseismic coupling presumably relates to spatial variations of frictional properties along the subduction interface and may also show up in the forearc morphology. To investigate this hypothesis, we compiled information on the extent of earthquake ruptures for the last 500 years and uplift rates derived from dated marine terraces along the South American coastline from central Peru to Southern Chile. We additionally calculated a new interseismic coupling model for that same area based on a compilation of GPS data. We show that the coastline geometry, characterized by the distance between the coast and the trench, the latitudinal variations of long-term uplift rates and the spatial pattern of interseismic coupling are correlated. Zones of faster and long-term permanent coastal uplift, evidenced by uplifted marine terraces, coincide with peninsulas, and also with areas of creep on the megathrust where slip is mostly aseismic and tend to arrest seismic ruptures. We conclude that spatial variations of frictional properties along the megathrust dictate the tectono-geomorphological evolution of the coastal zone and the extent of seismic ruptures along strike.

Additional Information

© 2017 American Geophysical Union. Received 10 FEB 2016; Accepted 21 JAN 2017; Accepted article online 25 JAN 2017; Published online 9 FEB 2017. This research project was led thanks to support of the Institut de Recherche pour le Développement (IRD). We thank T. Schildgen and two anonymous reviewers for constructive and critical comments of this manuscript. All data for this paper are properly cited and referred to in the reference list and available by contacting the corresponding author (marianne.saillard@ird.fr). We would like to dedicate this work to the memory of Luc Ortlieb.

Attached Files

Published - Saillard_et_al-2017-Tectonics.pdf

Supplemental Material - tect20530-sup-0001-2016TC004156_SI.docx

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