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Mechanical Implications of Creep and Partial Coupling on the World's Fastest Slipping Low-angle Normal Fault in Southeastern Papua New Guinea
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  • James B. Biemiller,
  • Carolyn Boulton,
  • Laura Wallace,
  • Susan Ellis,
  • Timothy Little,
  • Marcel Mizera,
  • André Niemeijer,
  • Luc L Lavier
James B. Biemiller
University of Texas at Austin

Corresponding Author:[email protected]

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Carolyn Boulton
Victoria University of Wellington
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Laura Wallace
GNS Science
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Susan Ellis
Geological and Nuclear Sciences
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Timothy Little
Victoria University of Wellington
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Marcel Mizera
Utrecht University
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André Niemeijer
Utrecht University
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Luc L Lavier
Department of Geological Sciences, Institute for Geophysics, University of Texas at Austin
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Abstract

We use densely spaced campaign GPS observations and laboratory friction experiments on fault rocks from one of the world’s most rapidly slipping low-angle normal faults, the Mai’iu fault in Papua New Guinea, to investigate the nature of interseismic deformation on active low-angle normal faults. GPS velocities reveal 8.3±1.2 mm/yr of horizontal extension across the Mai’iu fault, and are fit well by dislocation models with shallow fault locking (above 2 km depth), or by deeper locking (from ~5-16 km depth) together with shallower creep. Laboratory friction experiments show that gouges from the shallowest portion of the fault zone are predominantly weak and velocity-strengthening, while fault rocks deformed at greater depths are stronger and velocity-weakening. Evaluating the geodetic and friction results together with geophysical and microstructural evidence for mixed-mode seismic and aseismic slip at depth, we find that the Mai’iu fault is most likely strongly locked at depths of ~5-16 km and creeping updip and downdip of this region. Our results suggest that the Mai’iu fault and other active low-angle normal faults can slip in large (M > 7) earthquakes despite near-surface interseismic creep on frictionally stable clay-rich gouges.
Oct 2020Published in Journal of Geophysical Research: Solid Earth volume 125 issue 10. 10.1029/2020JB020117