Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Seismic slip on an upper-plate normal fault during a large subduction megathrust rupture


Quantification of stress accumulation and release during subduction zone seismic cycles requires an understanding of the distribution of fault slip during earthquakes. Reconstructions of slip are typically constrained to a single, known fault plane. Yet, slip has been shown to occur on multiple faults within the subducting plate1 owing to stress triggering2, resulting in phenomena such as earthquake doublets3. However, rapid stress triggering from the plate interface to faults in the overriding plate has not been documented. Here we analyse seismic data from the magnitude 7.1 Araucania earthquake that occurred in the Chilean subduction zone in 2011. We find that the earthquake, which was reported as a single event in global moment tensor solutions4,5, was instead composed of two ruptures on two separate faults. Within 12 s a thrust earthquake on the plate interface triggered a second large rupture on a normal fault 30 km away in the overriding plate. This configuration of partitioned rupture is consistent with normal-faulting mechanisms in the ensuing aftershock sequence. We conclude that plate interface rupture can trigger almost instantaneous slip in the overriding plate of a subduction zone. This shallow upper-plate rupture may be masked from teleseismic data, posing a challenge for real-time tsunami warning systems.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Location and single source solution.
Figure 2: Two-point-source solution.
Figure 3: Aftershock analysis.
Figure 4: Schematic interpretation of the Araucania earthquake rupture.

Similar content being viewed by others


  1. Lay, T., Duputel, Z., Ye, L. & Kanamori, H. The December 7, 2012 Japan Trench intraplate doublet (Mw 7.2, 7.1) and interactions between near-trench intraplate thrust and normal faulting. Phys. Earth Planet. Inter. 220, 73–78 (2013).

    Article  Google Scholar 

  2. Freed, A. M. Earthquake triggering by static, dynamic, and postseismic stress transfer. Annu. Rev. Earth Planet. Sci. 33, 335–367 (2004).

    Article  Google Scholar 

  3. Ammon, C. J., Kanamori, H. & Lay, T. A great earthquake doublet and seismic stress transfer cycle in the central Kuril islands. Nature 451, 561–565 (2008).

    Article  Google Scholar 

  4. National Earthquake Information Center M7.2–Araucania, Chile (United States Geological Survey, 2011);

  5. Ekström, G., Nettles, M. & Dziewoński, A. M. The global CMT project 2004–2010: Centroid-moment tensors for 13,017 earthquakes. Phys. Earth Planet. Inter. 200–201, 1–9 (2012).

    Article  Google Scholar 

  6. Moreno, M. et al. Toward understanding tectonic control on the Mw 8.8 2010 Maule Chile earthquake. Earth Planet. Sci. Lett. 321–322, 152–165 (2012).

    Article  Google Scholar 

  7. Hayes, G. P., Wald, D. J. & Johnson, R. L. Slab1. 0: A three-dimensional model of global subduction zone geometries. J. Geophys. Res. 117, B01302 (2012).

    Article  Google Scholar 

  8. Lay, T. et al. The 2009 Samoa–Tonga great earthquake triggered doublet. Nature 466, 964–968 (2010).

    Article  Google Scholar 

  9. Audin, L., Lacan, P., Tavera, H. & Bondoux, F. Upper plate deformation and seismic barrier in front of Nazca subduction zone: The Chololo Fault System and active tectonics along the Coastal Cordillera, southern Peru. Tectonophysics 459, 174–185 (2008).

    Article  Google Scholar 

  10. Melnick, D., Bookhagen, B., Strecker, M. R. & Echtler, H. P. Segmentation of megathrust rupture zones from fore-arc deformation patterns over hundreds to millions of years, Arauco peninsula, Chile. J. Geophys. Res. 114, B01407 (2009).

    Article  Google Scholar 

  11. Rietbrock, A. et al. Aftershock seismicity of the 2010 Maule Mw = 8.8, Chile, earthquake: Correlation between co-seismic slip models and aftershock distribution? Geophys. Res. Lett. 39, L08310 (2012).

    Article  Google Scholar 

  12. Moreno, M. S., Bolte, J., Klotz, J. & Melnick, D. Impact of megathrust geometry on inversion of coseismic slip from geodetic data: Application to the 1960 Chile earthquake. Geophys. Res. Lett. 36, L16310 (2009).

    Article  Google Scholar 

  13. Sokos, E. & Zahradnik, J. A Matlab GUI for use with ISOLA Fortran codes. Users’ Guide (2006).

  14. Zahradnik, J., Serpetsidaki, A., Sokos, E. & Tselentis, G.-A. Iterative deconvolution of regional waveforms and a double-event interpretation of the 2003 Lefkada Earthquake, Greece. Bull. Seismol. Soc. Am. 95, 159–172 (2005).

    Article  Google Scholar 

  15. Hicks, S. P., Rietbrock, A., Ryder, I. M. A., Lee, C.-S. & Miller, M. Anatomy of a megathrust: The 2010 M8.8 Maule, Chile earthquake rupture zone imaged using seismic tomography. Earth Planet. Sci. Lett. 405, 142–155 (2014).

    Article  Google Scholar 

  16. Haberland, C., Rietbrock, A., Lange, D., Bataille, K. & Dahm, T. Structure of the seismogenic zone of the southcentral Chilean margin revealed by local earthquake traveltime tomography. J. Geophys. Res. 114, B01317 (2009).

    Article  Google Scholar 

  17. Zahradnik, J. & Sokos, E. The Mw 7.1 Van, Eastern Turkey, earthquake 2011: Two-point source modelling by iterative deconvolution and non-negative least squares. Geophys. J. Int. 196, 522–538 (2014).

    Article  Google Scholar 

  18. Komatitsch, D., Erlebacher, G., Göddeke, D. & Michéa, D. High-order finite-element seismic wave propagation modeling with MPI on a large GPU cluster. J. Comput. Phys. 229, 7692–7714 (2010).

    Article  Google Scholar 

  19. Hicks, S. P., Nippress, S. E. & Rietbrock, A. Sub-slab mantle anisotropy beneath south-central Chile. Earth Planet. Sci. Lett. 357, 203–213 (2012).

    Article  Google Scholar 

  20. Hardebeck, J. L. Coseismic and postseismic stress rotations due to great subduction zone earthquakes. Geophys. Res. Lett. 39, L21313 (2012).

    Article  Google Scholar 

  21. Blaser, L., Krüger, F., Ohrnberger, M. & Scherbaum, F. Scaling relations of earthquake source parameter estimates with special focus on subduction environment. Bull. Seismol. Soc. Am. 100, 2914–2926 (2010).

    Article  Google Scholar 

  22. González, G. et al. Upper plate reverse fault reactivation and the unclamping of the megathrust during the 2014 northern Chile earthquake sequence. Geology 43, 671–674 (2015).

    Article  Google Scholar 

  23. Singh, S. C. et al. Evidence of active backthrusting at the NE margin of Mentawai Islands, SW Sumatra. Geophys. J. Int. 180, 703–714 (2010).

    Article  Google Scholar 

  24. Geersen, J., Völker, D., Behrmann, J. H., Reichert, C. & Krastel, S. Pleistocene giant slope failures offshore Arauco Peninsula, Southern Chile. J. Geol. Soc. Lond. 168, 1237–1248 (2011).

    Article  Google Scholar 

  25. Frohlich, C. Triangle diagrams: Ternary graphs to display similarity and diversity of earthquake focal mechanisms. Phys. Earth Planet. Inter. 75, 193–198 (1992).

    Article  Google Scholar 

  26. Hayes, G. P. et al. Seismotectonic framework of the 2010 February 27 Mw 8.8 Maule, Chile earthquake sequence. Geophys. J. Int. 195, 1034–1051 (2013).

    Article  Google Scholar 

  27. Melnick, D. & Echtler, H. P. The Andes 565–568 (Springer, 2006).

    Book  Google Scholar 

  28. Quintero, R., Zahradnik, J. & Sokos, E. Near-regional CMT and multiple-point source solution of the September 5, 2012, Nicoya, Costa Rica Mw 7.6 (GCMT) earthquake. J. South Am. Earth Sci. 55, 155–165 (2014).

    Article  Google Scholar 

  29. Sokos, E. & Zahradnik, J. Evaluating centroid-moment-tensor uncertainty in the new version of ISOLA software. Seismol. Res. Lett. 84, 656–665 (2013).

    Article  Google Scholar 

  30. Casarotti, E. et al. in Proceedings of the 16th International Meshing Roundtable 579–597 (Springer, 2008).

    Book  Google Scholar 

Download references


We are grateful to all field crews from partner organizations who participated in the deployment and servicing of seismic instruments used in this study. We thank J. Zahradník and E. Sokos for their assistance in setting up the ISOLA code. S.P.H. is financially supported by a NERC studentship (NE/J50015X/1).

Author information

Authors and Affiliations



S.P.H. carried out the single and multiple point-source inversions, as well as the moment tensor inversion and aftershock relocations. S.P.H. wrote the manuscript, interpreted the results, and generated all figures. A.R. carried out the 3D full waveform simulations, wrote the manuscript, and interpreted the results.

Corresponding authors

Correspondence to Stephen P. Hicks or Andreas Rietbrock.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 2551 kb)

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Hicks, S., Rietbrock, A. Seismic slip on an upper-plate normal fault during a large subduction megathrust rupture. Nature Geosci 8, 955–960 (2015).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing