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Locking on a megathrust as a cause of distributed faulting and fault-jumping earthquakes


Seismicity on large faults is often characterized in terms of an independent recurrence time and magnitude distribution, which forms the basis for calculating future earthquake probabilities. The underlying assumption is that the driving mechanism for earthquakes on any particular fault is uniquely linked to that fault, determined by the rate of long-term creep on its deeper extension. However, our modelling of nearly 20 years of Global Positioning System data along the obliquely converging plate boundary in New Zealand shows that interseismic stress accumulation can be independent of the properties of the numerous crustal faults and controlled by locking on the megathrust. In this way, the interseismic driving mechanism for large crustal earthquakes is not linked directly to the individual major faults that rupture. This scenario predicts large-magnitude earthquakes with complex multifault ruptures in broad zones that ‘jump’ from fault to fault, following the contours of stress/strain loading. This can explain the November 2016 Mw7.8 Kaikoura earthquake that shattered the plate boundary in central New Zealand. Repeated episodes of this would create the observed complex array of active faults with the appearance of coherent slip. Our analysis opens up the possibility to use long-term Global Positioning System data to identify this type of earthquake behaviour.

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Fig. 1: Topography/bathymetry, tectonic setting and strain-rate field in New Zealand along the boundary between the Pacific and Australian Plates.
Fig. 2: 2D elastic model for interseismic deformation along profile 3 (Fig. 1b) across the New Zealand plate boundary (N = 70, free parameters = 7).
Fig. 3: Trace of megathrust locking line, GPS-derived strain rate field and Mw7.8 2016 Kaikōura Earthquake ruptures.
Fig. 4: 3D perspective view of the modelled geometry of the deep slipping surfaces that drive interseismic deformation (see Figs. 2 and 3).

Data availability

All of the data used in this article are from publications fully cited in the text. Extensive use of Generic Mapping Tools was made to process data and create the figures.


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This paper is part of a wider project funded through the New Zealand Marsden Fund, Earthquake Commission and Victoria University of Wellington graduate scholarships. J.D.P.M. was supported by the National Research Foundation of Singapore (award NRF-NRFF2013-04) at the Earth Observatory of Singapore. Data made publicly available through GeoNet ( and GNS Science were used in this work. We thank R. Burgmann and E. Lindsey for their insightful reviews that greatly improved the manuscript.

Author information




S.L. carried out the strain rate analysis and 2D elastic modelling, wrote the manuscript and created the main figures. R.A. guided the statistical analysis and J.D.P.M. wrote the computer code for the 3D modelling; both made comments on the manuscript.

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Correspondence to Simon Lamb.

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Supplementary Table 1 and Supplementary Figures 1–9.

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Lamb, S., Arnold, R. & Moore, J.D.P. Locking on a megathrust as a cause of distributed faulting and fault-jumping earthquakes. Nature Geosci 11, 871–875 (2018).

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