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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
Author(s) -
Biemiller James,
Boulton Carolyn,
Wallace Laura,
Ellis Susan,
Little Timothy,
Mizera Marcel,
Niemeijer Andre,
Lavier Luc
Publication year - 2020
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2020jb020117
Subject(s) - geology , slipping , seismology , slip (aerodynamics) , creep , fault (geology) , normal fault , geodetic datum , san andreas fault , new guinea , geodesy , petrology , geometry , materials science , physics , mathematics , composite material , thermodynamics , history , ethnology
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/year 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 w > 7) earthquakes despite near‐surface interseismic creep on frictionally stable clay‐rich gouges.