Article

Corrugated megathrust revealed offshore from Costa Rica

  • Nature Geosciencevolume 11pages197202 (2018)
  • doi:10.1038/s41561-018-0061-4
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Abstract

Exhumed faults are rough, often exhibiting topographic corrugations oriented in the direction of slip; such features are fundamental to mechanical processes that drive earthquakes and fault evolution. However, our understanding of corrugation genesis remains limited due to a lack of in situ observations at depth, especially at subducting plate boundaries. Here we present three-dimensional seismic reflection data of the Costa Rica subduction zone that image a shallow megathrust fault characterized by corrugated, and chaotic and weakly corrugated topographies. The corrugated surfaces extend from near the trench to several kilometres down-dip, exhibit high reflection amplitudes (consistent with high fluid content/pressure) and trend 11–18° oblique to subduction, suggesting 15 to 25 mm yr1 of trench-parallel slip partitioning across the plate boundary. The corrugations form along portions of the megathrust with greater cumulative slip and may act as fluid conduits. In contrast, weakly corrugated areas occur adjacent to active plate bending faults where the megathrust has migrated up-section, forming a nascent fault surface. The variations in megathrust roughness imaged here suggest that abandonment and then reestablishment of the megathrust up-section transiently increases fault roughness. Analogous corrugations may exist along significant portions of subduction megathrusts globally.

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Change history

  • Correction 26 March 2018

    In the version of this Article originally published, in Fig. 1a the Nicoya Peninsula, Osa Peninsula and Burica Peninsula were incorrectly labelled as the Nicoya Plate, Osa Plate and Burica Plate, respectively. This has been corrected in the online versions.

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Acknowledgements

This work was supported by US National Science Foundation grants OCE-0851380 and OCE-1154635. We thank dGB Earth Sciences for free access to OpendTect Pro and associated commercial plugins.

Author information

Affiliations

  1. Department of Earth and Planetary Sciences, University of California, Santa Cruz, Santa Cruz, CA, USA

    • Joel H. Edwards
    • , Eli A. Silver
    • , Emily E. Brodsky
    • , Ruby Wood
    •  & Kristina Okamoto
  2. Pacific Coastal and Marine Science Center, US Geological Survey, Santa Cruz, CA, USA

    • Jared W. Kluesner
    •  & Daniel S. Brothers
  3. Institute for Geophysics, University of Texas at Austin, Austin, TX, USA

    • Nathan L. Bangs
  4. Earth and Planetary Sciences, McGill University, Montreal, Canada

    • James D. Kirkpatrick

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Contributions

J.W.K., E.A.S. and N.L.B. obtained financial support for the marine seismic reflection program and collected and processed the seismic data. J.H.E. applied post processing, performed amplitude-driven tracking and extracted geometric attributes along the shallow megathrust. E.E.B. called attention to the corrugations. D.S.B. and J.D.K. furthered analysis of the corrugations. R.W. and K.O. extracted the scale of the corrugations. J.H.E. wrote the manuscript with contributions from all other authors.

Competing financial interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Joel H. Edwards.