Letter | Published:

Lower edge of locked Main Himalayan Thrust unzipped by the 2015 Gorkha earthquake

Nature Geoscience volume 8, pages 708711 (2015) | Download Citation

Abstract

Large earthquakes are thought to release strain on previously locked faults. However, the details of how earthquakes are initiated, grow and terminate in relation to pre-seismically locked and creeping patches is unclear1,2,3,4. The 2015 Mw 7.8 Gorkha, Nepal earthquake occurred close to Kathmandu in a region where the prior pattern of fault locking is well documented5. Here we analyse this event using seismological records measured at teleseismic distances and Synthetic Aperture Radar imagery. We show that the earthquake originated northwest of Kathmandu within a cluster of background seismicity that fringes the bottom of the locked portion of the Main Himalayan Thrust fault (MHT). The rupture propagated eastwards for about 140 km, unzipping the lower edge of the locked portion of the fault. High-frequency seismic waves radiated continuously as the slip pulse propagated at about 2.8 km s−1 along this zone of presumably high and heterogeneous pre-seismic stress at the seismic–aseismic transition. Eastward unzipping of the fault resumed during the Mw 7.3 aftershock on 12 May. The transfer of stress to neighbouring regions during the Gorkha earthquake should facilitate future rupture of the areas of the MHT adjacent and updip of the Gorkha earthquake rupture.

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Acknowledgements

Sentinel-1A data are provided by the European Space Agency. T.W. thanks J. Kim from SMU for help in processing the SAR data. We also thank R. Bürgmann for comments on an earlier version of this study. J.-Ph.A. thanks the BP Foundation and the Royal Society for support.

Author information

Affiliations

  1. Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, UK

    • Jean-Philippe Avouac
  2. Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, 595 Charles Young Drive East, Box 951567, Los Angeles, California 950095, USA

    • Lingsen Meng
  3. Earth Observatory of Singapore, Nanyang Technological University, N2-01A-108, 50 Nanyang Avenue, Singapore 639798, Singapore

    • Shengji Wei
  4. Huffington Department of Earth Sciences, Southern Methodist University, PO Box 750395, Dallas, Texas 75275-0395, USA

    • Teng Wang
  5. Seismological Laboratory, Geology and Planetary Science Division, California Institute of Technology, 1200 E. California Boulevard, Pasadena, California 91125, USA

    • Jean-Paul Ampuero

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Contributions

J.-Ph.A. coordinated the research and wrote the article. L.M. and J.-P.A. carried out the back-projection. S.W. carried out the finite source modelling. T.W. carried out the SAR offset measurements. All authors contributed to the interpretation and writing of the article.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Jean-Philippe Avouac.

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DOI

https://doi.org/10.1038/ngeo2518

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