ABSTRACT The Indo-Australian plate is undergoing distributed internal deformation caused by the lateral transition along its northern boundary—from an environment of continental collision to

an island arc subduction zone1,2. On 11 April 2012, one of the largest strike-slip earthquakes ever recorded (seismic moment magnitude _M_w 8.7) occurred about 100–200 kilometres southwest

of the Sumatra subduction zone. Occurrence of great intraplate strike-slip faulting located seaward of a subduction zone is unusual. It results from northwest–southeast compression within

the plate caused by the India–Eurasia continental collision to the northwest, together with northeast–southwest extension associated with slab pull stresses as the plate underthrusts Sumatra

trending west-northwest to east-southeast (WNW–ESE), and then bilateral rupture was triggered on an orthogonal left-lateral strike-slip fault trending north-northeast to south-southwest

(NNE–SSW) that crosses the first fault. This was followed by westward rupture on a second WNW–ESE strike-slip fault offset about 150 kilometres towards the southwest from the first fault.

Finally, rupture was triggered on another _en échelon_ WNW–ESE fault about 330 kilometres west of the epicentre crossing the Ninetyeast ridge. The great aftershock, with an epicentre located

185 kilometres to the SSW of the mainshock epicentre, ruptured bilaterally on a NNE–SSW fault. The complex faulting limits our resolution of the slip distribution. These great ruptures on a

lattice of strike-slip faults that extend through the crust and a further 30–40 kilometres into the upper mantle represent large lithospheric deformation that may eventually lead to a

localized boundary between the Indian and Australian plates. Access through your institution Buy or subscribe This is a preview of subscription content, access via your institution ACCESS

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institutional subscriptions * Read our FAQs * Contact customer support SIMILAR CONTENT BEING VIEWED BY OTHERS FAST AND SLOW INTRAPLATE RUPTURES DURING THE 19 OCTOBER 2020 MAGNITUDE 7.6

SHUMAGIN EARTHQUAKE Article Open access 10 April 2023 COMPLEX MULTI-FAULT RUPTURE AND TRIGGERING DURING THE 2023 EARTHQUAKE DOUBLET IN SOUTHEASTERN TÜRKIYE Article Open access 09 September

2023 THRUST-DOMINATED UNILATERAL RUPTURE OF A BLIND LISTRIC FAULT ASSOCIATED WITH THE 2024 HUALIEN EARTHQUAKE Article Open access 28 December 2024 REFERENCES * Minster, J. B. & Jordan,

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California (Mw 7.3) earthquake. _Bull. Seismol. Soc. Am._ 84, 735–750 (1994) Google Scholar  Download references ACKNOWLEDGEMENTS We thank H. Kanamori, Z. Duputel and G. Hayes for

discussions and exchanges of information about this event. A. Hutko provided early short-period back-projection results. We thank R. Abercrombie for comments on this paper. This work made

use of GMT and SAC software and Federation of Digital Seismic Networks (FDSN) seismic data. The Incorporated Research Institutions for Seismology (IRIS) Data Management System (DMS), the

European ORFEUS Data Center and the NIED F-net Data Centre were used to access the data. This work was supported by NSF grant EAR0635570 (T.L.) and EAR0951558 (K.D.K.). AUTHOR INFORMATION

AUTHORS AND AFFILIATIONS * Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, 95064, California, USA Han Yue & Thorne Lay * Department of

Geology and Geophysics, University of Utah, Salt Lake City, 84112, Utah, USA Keith D. Koper Authors * Han Yue View author publications You can also search for this author inPubMed Google

Scholar * Thorne Lay View author publications You can also search for this author inPubMed Google Scholar * Keith D. Koper View author publications You can also search for this author

inPubMed Google Scholar CONTRIBUTIONS H.Y. contributed to the surface wave back-projections and finite fault modelling; K.D.K. performed the short-period back-projections; and T.L. performed

finite-fault inversions and guided the synthesis. CORRESPONDING AUTHOR Correspondence to Thorne Lay. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no competing financial

interests. SUPPLEMENTARY INFORMATION SUPPLEMENTARY INFORMATION This file contains Supplementary Figures 1-7 and full legends for Supplementary Movies 1 -2. (PDF 2244 kb) SUPPLEMENTARY MOVIE

1 This movie shows animations of the short-period back-projections from European and Japanese (F-net) stations for the Mw 8.7 event - see Supplementary Information file for full legend. (MOV

4839 kb) SUPPLEMENTARY MOVIE 2 This movie shows animations of the short-period back-projections from European and Japanese (F-net) stations for the Mw 8.2 event - see Supplementary

Information file for full legend. (MOV 3512 kb) POWERPOINT SLIDES POWERPOINT SLIDE FOR FIG. 1 POWERPOINT SLIDE FOR FIG. 2 POWERPOINT SLIDE FOR FIG. 3 POWERPOINT SLIDE FOR FIG. 4 RIGHTS AND

PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Yue, H., Lay, T. & Koper, K. _En échelon_ and orthogonal fault ruptures of the 11 April 2012 great intraplate

earthquakes. _Nature_ 490, 245–249 (2012). https://doi.org/10.1038/nature11492 Download citation * Received: 06 May 2012 * Accepted: 07 August 2012 * Published: 26 September 2012 * Issue

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