Multi-timescale mechanics of an active low-angle normal fault

Detachment faults dipping 7.0) earthquakes (Chapter 4). Velocities from a newly installed network of densely spaced campaign GPS sites reveal horizontal extension rates of 8.3±1.2 mm/yr (~8-11 mm/yr dip-slip) on the Mai’iu fault (Chapter 5). Laboratory friction experiments on exhumed Mai’iu fault rocks showing depth-dependent transitions in frictional stability help constrain inversions of kinematic models of the GPS velocities indicating that the Mai’iu fault is more strongly locked at ~5-16 km depth and creeping interseismically above 5 km depth. This result suggests that large (Mw > 7.0) earthquakes nucleate downdip of the low-angle portion of the Mai’iu fault and can propagate to the surface along the shallowly-dipping segment and/or more steeply-dipping splay faults in its hanging wall. In contrast to previous studies suggesting that active low-angle normal faults predominantly creep aseismically, this work implies that the active Mai’iu low-angle normal fault slips in infrequent large earthquakes accompanied by some shallow interseismic creep.Geological Science