New insights into the tectonic inversion of North Canterbury and the regional structural context of the 2010–2011 Canterbury earthquake sequence, New Zealand

The 2010–2011 Canterbury earthquake sequence highlighted the existence of previously unknown active faults beneath the North Canterbury plains and Pegasus Bay, South Island, New Zealand. We provide new insights into the geometry and kinematics of ongoing deformation by analyzing marine seismic data to produce new maps of regional faults and cross‐sectional reconstructions of deformation history. Active faulting and folding extends up to 30 km offshore, and involves reactivation of sets of Late Cretaceous‐Paleogene normal faults under NW‐SE tectonic compression. The active faults consist predominantly of NE‐SW striking, SE‐dipping reverse faults, and less commonly E‐W to NW‐SE faults suitably oriented for strike‐slip reactivation. Additionally, newly developing reverse faults obliquely segment and overprint the inherited basement fabric and impose geometric and kinematic complexities revealed by mapping and reverse displacement profiles of markers. The Quaternary reverse slip rates decrease from 0.1–0.3 mm/yr beneath northern Pegasus Bay to <0.05 mm/yr approaching Banks Peninsula. Fault growth modeling involving trishear fault‐propagation folding mechanisms successfully restores an evolutionary sequence of progressive fault inversion, revealing a history of reactivated individual faults. Tectonic inversion and overprinting processes beneath Pegasus Bay are immature and <1.2 ± 0.4 Ma old, with no evidence of systematic spatial migration of deformation. Our marine data analyses give insights into the structural context of the 2010–2011 Canterbury earthquake sequence, while the combined onshore to offshore data provide an excellent illustration of fault growth associated with immature inversion tectonics, in which selective fault reactivation results from compressive stress imposed across a complex network of inherited faults.