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Sci Adv. 2019 Oct 2;5(10):eaax5703. doi: 10.1126/sciadv.aax5703. eCollection 2019 Oct.

Unusual kinematics of the Papatea fault (2016 Kaikōura earthquake) suggest anelastic rupture.

Author information

1
School of Earth and Ocean Sciences, University of Victoria, Victoria, BC, Canada.
2
Department of Geophysics, Colorado School of Mines, 1500 Illinois St., Golden, CO, USA.
3
GNS Science, PO Box 30 368, Lower Hutt 5040, New Zealand.
4
Department of Computer Sciences, University of Victoria, Victoria, BC, Canada.

Abstract

A key paradigm in seismology is that earthquakes release elastic strain energy accumulated during an interseismic period on approximately planar faults. Earthquake slip models may be further informed by empirical relations such as slip to length. Here, we use differential lidar to demonstrate that the Papatea fault-a key element within the 2016 Mw 7.8 Kaikōura earthquake rupture-has a distinctly nonplanar geometry, far exceeded typical coseismic slip-to-length ratios, and defied Andersonian mechanics by slipping vertically at steep angles. Additionally, its surface deformation is poorly reproduced by elastic dislocation models, suggesting the Papatea fault did not release stored strain energy as typically assumed, perhaps explaining its seismic quiescence in back-projections. Instead, it slipped in response to neighboring fault movements, creating a localized space problem, accounting for its anelastic deformation field. Thus, modeling complex, multiple-fault earthquakes as slip on planar faults embedded in an elastic medium may not always be appropriate.

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