Letter | Published:

A mixed seismic–aseismic stress release episode in the Andean subduction zone

Nature Geoscience volume 9, pages 150154 (2016) | Download Citation


In subduction zones, stress is released by earthquakes and transient aseismic slip. The latter falls into two categories: slow slip and afterslip. Slow-slip events emerge spontaneously during the interseismic phase, and show a progressive acceleration of slip with a negligible contribution of synchronous tremors or microseismicity to the energy, or moment release1,2,3,4,5,6,7,8,9,10,11,12. In contrast, afterslip occurs immediately after large and moderate earthquakes, decelerates over time, and releases between 20 and 400% of the moment released by the preceding earthquake13,14,15,16,17,18. Here we use seismic and GPS data to identify transient aseismic slip that does not fit into either of these categories. We document a seismic–aseismic slip sequence which occurred at shallow depths along a weakly coupled part of the Andean subduction zone19 in northern Peru and lasted seven months. The sequence generated several moderate earthquakes that together account for about 25% of the total moment released during the full sequence, equivalent to magnitude 6.7. Transient slip immediately followed two of the earthquakes, with slip slowing at a logarithmic rate. Considered separately, the moment released by transient slip following the second earthquake was more than 1,000% of the moment released during the earthquake itself, a value incompatible with classical models of afterslip. Synchronous seismic swarms and aseismic slip may therefore define a stress-release process that is distinct from slow-slip events and afterslip.

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This work has been funded by the ANR (Agence Nationale de la Recherche, contract number ANR-07-BLAN-0143-01) and has continuously been supported by the IRD (Institut de Recherche pour le Développement). We thank J. P. Ampuero from Caltech for the use of broadband seismic data from a temporary network in the frame of the Sisnort-08 project. J.C.V.-L. acknowledges support provided by the IRD-DSF through a PhD grant.

Author information

Author notes

    • T. Tran

    Present address:  National University of Civil Engineering, 55, Giai Phong Road, Hai Ba Trung District, Hanoi, Vietnam.


  1. Instituto Geofísico del Perú, Calle Badajoz 169, Urbanización Mayorazgo IV Etapa, Ate, 15012 Lima 03, Perú

    • J. C. Villegas-Lanza
    •  & H. Tavera
  2. Geoazur, IRD, Université de Nice Sophia-Antipolis, Observatoire de la Côte d’Azur, CNRS, 250, rue A. Einstein, 06560 Valbonne, France

    • J. C. Villegas-Lanza
    • , J.-M. Nocquet
    • , T. Tran
    • , X. Martin
    •  & M. Chlieh
  3. Sorbonne Universités, UPMC Univ Paris 06, CNRS, Institut des Sciences de la Terre de Paris (ISTeP), 4, Place Jussieu, 75005 Paris, France

    • F. Rolandone
  4. Institut de Physique du globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, UMR 7154 CNRS, 75238 Paris cedex 05, France

    • M. Vallée
  5. Géosciences Environnement Toulouse, Université Paul Sabatier, IRD, CNRS, Observatoire Midi-Pyrénées, 31400 Toulouse, France

    • F. Bondoux


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J.C.V.-L. and J.-M.N. carried out fieldwork, GPS analysis and slip inversion; J.C.V.-L. performed the seismicity analysis; J.-M.N. and F.R. performed the rate-and-state calculations; M.V. conducted the source time functions analysis; M.C., F.B. and X.M. carried out GPS fieldwork; H.T. provided seismological data; T.T. performed GPS analysis; J.-M.N., F.R. and J.C.V.-L. wrote the paper. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to J. C. Villegas-Lanza or J.-M. Nocquet.

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