In April 2015, the lower locked portion of the Main Himalayan Thrust ruptured beneath Nepal, causing the disastrous Mw 7.8 Gorkha earthquake. Elucidating the enigmatic geometry of this plate boundary fault is important for understanding the nucleation and arrest of large earthquake ruptures as well as the seismic hazard, topography and tectonics of the Himalaya. Here we interpret the geometry of the Main Himalayan Thrust from the spatial distribution and rupture patterns of a dynamic sequence of aftershocks following the Gorkha earthquake, which were recorded by a rapidly deployed dense seismic network. We find that the thrust comprises two north-dipping subhorizontal planes that are connected by a system of bounded imbricate thrust faults; this structure is known as a duplex. We propose that this duplex acts as an impediment to plate convergence and accommodates tectonic stress along its complex system of faults. Such a prominent structure to the Main Himalayan Thrust is consistent with surface geological studies but challenges geophysically derived conventional models with simpler geometries.
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The waveform dataset and metadata are unrestricted and freely available through the IRIS Data Management Center website (https://ds.iris.edu/ds/nodes/dmc/) under network code ‘XQ: Rapid Response to the Mw 7.9 earthquake of April 25, 2015 in Nepal’. The data that support the findings of this study can be obtained by referring to the supplementary information or contacting the author.
Codes used to generate the results of this study are available through the contact information from the original publications. Requests for further materials should be directed to the corresponding author.
Bilham, R. Seismology: raising Kathmandu. Nat. Geosci. 8, 582–584 (2015).
Bilham, R., Gaur, V. K. & Molnar, P. Himalayan seismic hazard. Science 293, 1442–1444 (2001).
Dal Zilio, L., Van Dinther, Y., Gerya, T. & Avouac, J. P. Bimodal seismicity in the Himalaya controlled by fault friction and geometry. Nat. Commun. 10, 48 (2019).
Chen, W. P. & Molnar, P. Seismic moments of major earthquakes and the average rate of slip in central Asia. J. Geophys. Res. 80, 2945–2969 (1977).
Bilham, R. Location and magnitude of the 1833 Nepal earthquake and its relation to the rupture zones of contiguous great Himalayan earthquakes. Curr. Sci. 69, 101–128 (1995).
Ambraseys, N. N. & Douglas, J. Magnitude calibration of north Indian earthquakes. Geophys. J. Int. 159, 165–206 (2004).
Sapkota, S. N. et al. Primary surface ruptures of the great Himalayan earthquakes in 1934 and 1255. Nat. Geosci. 6, 71–76 (2013).
Bilham, R. Himalayan earthquakes: a review of historical seismicity and early 21st century slip potential. Geol. Soc. Spec. Publ. 483, 423–482 (2019).
Mugnier, J. L. et al. Segmentation of the Himalayan megathrust around the Gorkha earthquake (25 April 2015) in Nepal. J. Asian Earth Sci. 141, 236–252 (2017).
Martin, S. S., Hough, S. E. & Hung, C. Ground motions from the 2015 M w 7.8 Gorkha, Nepal, earthquake constrained by a detailed assessment of macroseismic data. Seismol. Res. Lett. 86, 1524–1532 (2015).
Avouac, J. P., Meng, L., Wei, S., Wang, T. & Ampuero, J. P. Lower edge of locked Main Himalayan Thrust unzipped by the 2015 Gorkha earthquake. Nat. Geosci. 8, 708–711 (2015).
Elliott, J. R. et al. Himalayan megathrust geometry and relation to topography revealed by the Gorkha earthquake. Nat. Geosci. 9, 174–180 (2016).
Grandin, R. et al. Rupture process of the M w=7.9 2015 Gorkha earthquake (Nepal): insights into Himalayan megathrust segmentation. Geophys. Res. Lett. 42, 8373–8383 (2015).
Gualandi, A. et al. Pre- and post-seismic deformation related to the 2015, M w7.8 Gorkha earthquake, Nepal. Tectonophysics 714, 90–106 (2017).
Adhikari, L. B. et al. The aftershock sequence of the 2015 April 25 Gorkha-Nepal earthquake. Geophys. J. Int. 203, 2119–2124 (2015).
Khanal, S., Robinson, D. M., Kohn, M. J. & Mandal, S. Evidence for a far-traveled thrust sheet in the Greater Himalayan thrust system, and an alternative model to building the Himalaya. Tectonics 34, 31–52 (2015).
Robinson, D. M. & Martin, A. J. Reconstructing the Greater Indian margin: a balanced cross section in central Nepal focusing on the Lesser Himalayan duplex. Tectonics 33, 2143–2168 (2014).
Decelles, P. G. et al. Stratigraphy, structure, and tectonic evolution of the Himalayan fold-thrust belt in western Nepal. Tectonics 20, 487–509 (2001).
Hubbard, J. et al. Structural segmentation controlled the 2015 M w 7.8 Gorkha earthquake rupture in Nepal. Geology 44, 639–642 (2016).
Wobus, C., Heimsath, A., Whipple, K. & Hodges, K. Active out-of-sequence thrust faulting in the central Nepalese Himalaya. Nature 434, 1008–1011 (2005).
Bollinger, L. et al. Thermal structure and exhumation history of the Lesser Himalaya in central Nepal. Tectonics 23, TC5015 (2004).
Duputel, Z. et al. The 2015 Gorkha earthquake: a large event illuminating the Main Himalayan Thrust fault. Geophys. Res. Lett. 43, 2517–2525 (2016).
Whipple, K. X., Shirzaei, M., Hodges, K. V. & Arrowsmith, J. R. Active shortening within the Himalayan orogenic wedge implied by the 2015 Gorkha earthquake. Nat. Geosci. 9, 711–716 (2016).
Gao, R. et al. Crustal-scale duplexing beneath the Yarlung Zangbo suture in the western Himalaya. Nat. Geosci. 9, 555–560 (2016).
Nábělek, J. et al. Underplating in the Himalaya–Tibet collision zone revealed by the Hi-CLIMB experiment. Science 325, 1371–1374 (2009).
Lemonnier, C. et al. Electrical structure of the Himalaya of central Nepal: high conductivity around the mid-crustal ramp along the MHT. Geophys. Res. Lett. 26, 3261–3264 (1999).
Karplus, M. S. et al. Aftershocks of the M7.8 Gorkha (Nepal) earthquake: early results from Project NAMASTE. Am. Geophys. Union 2015, abstr. S41D-07 (2015).
WaldHauser, F. & Ellsworth, W. L. A double-difference earthquake location algorithm: method and application to the northern Hayward fault, California. Bull. Seismol. Soc. Am. 90, 1353–1368 (2000).
Pandey, M. R., Tandukar, R. P., Avouac, J. P., Lave, J. & Massot, J. P. Interseismic strain accumulation on the Himalayan Crustal RAMP (Nepal). Geophys. Res. Lett. 22, 751–754 (1995).
Ader, T. et al. Convergence rate across the Nepal Himalaya and interseismic coupling on the Main Himalayan Thrust: implications for seismic hazard. J. Geophys. Res. Solid Earth 117, B04403 (2012).
Bettinelli, P. et al. Plate motion of India and interseismic strain in the Nepal Himalaya from GPS and DORIS measurements. J. Geod. 80, 567–589 (2006).
Hermann, R. B. & Ammon, C. J. Computer programs in seismology: an evolving tool for instruction and research. Seismol. Res. Lett. 84, 1081–1088 (2013).
Dziewonski, A. M., Chou, T. A. & Woodhouse, J. H. Determination of earthquake source parameters from waveform data for studies of global and regional seismicity. J. Geophys. Res. Solid Earth 86, 2825–2852 (1981).
Bai, L. et al. Lateral variation of the Main Himalayan Thrust controls the rupture length of the 2015 Gorkha Earthquake in Nepal. Sci. Adv. 5, eaav0723 (2019).
Khanal, S. & Robinson, D. M. Upper crustal shortening and forward modeling of the Himalayan thrust belt along the Budhi-Gandaki River, central Nepal. Int. J. Earth Sci. 102, 1871–1891 (2013).
Bilham, R., Larson, K. & Freymueller, J. GPS measurements of present-day convergence across the Nepal Himalaya. Nature 386, 61–64 (1997).
Cattin, R. & Avouac, J. P. Modeling mountain building and the seismic cycle in the Himalaya of Nepal. J. Geophys. Res. Solid Earth 105, 13389–13407 (2000).
Robinson, D. M. & McQuarrie, N. Pulsed deformation and variable slip rates within the central Himalayan thrust belt. Lithosphere 4, 449–464 (2012).
Mendoza, M. M., Ghosh, A. & Rai, S. S. Dynamic triggering of small local earthquakes in the central Himalaya. Geophys. Res. Lett. 43, 9581–9587 (2016).
Ross, Z. E., White, M. C., Vernon, F. L. & Ben-Zion, Y. An improved algorithm for real-time S-wave picking with application to the (augmented) ANZA network in Southern California. Bull. Seismol. Soc. Am. 106, 2013–2022 (2016).
Paige, C. C. & Saunders, M. A. LSQR: an algorithm for sparse linear equations and sparse least squares. ACM Trans. Math. Softw. 8, 43–71 (1982).
Wiemer, S. A software package to analyze seismicity: ZMAP. Seismol. Res. Lett. 72, 373–382 (2001).
We thank the Department of Mines and Geology in Nepal for the opportunity to collaborate on science that will help build communities that are more resilient to future earthquakes. This experiment was made possible by the field crew who helped install and maintain the seismic network, including C. Timsina, D. R. Tiwari, M. Pant, K. Pandey, N. Thapa, J. Braunmiller, K. Galvan, V. Kuna, J. Nakai, E. Patlan and many more Nepalese geologists and geophysicists. Special thanks to J. Nábělek for participating in the fieldwork and many stimulating discussions. We thank D. Robinson and D. Hazarika for their constructive comments, which helped to greatly improve the manuscript. The seismic instruments were provided by IRIS through the PASSCAL Instrument Center at New Mexico Tech and participating universities. This collaborative project is funded by the NSF-RAPID and NSF Geophysics programmes, award numbers 1620655 and 1546622.
The authors declare no competing interests.
Peer review information Primary Handling Editor(s): Melissa Plail; Stefan Lachowycz.
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Mendoza, M.M., Ghosh, A., Karplus, M.S. et al. Duplex in the Main Himalayan Thrust illuminated by aftershocks of the 2015 Mw 7.8 Gorkha earthquake. Nat. Geosci. 12, 1018–1022 (2019) doi:10.1038/s41561-019-0474-8
3D Fault Structure Inferred from a Refined Aftershock Catalog for the 2015 Gorkha Earthquake in Nepal
Bulletin of the Seismological Society of America (2019)