STRUCTURAL STYLES OF TRANSPRESSIONAL DEFORMATION ALONG THE MARGIN OF THE NEW ZEALAND PLATE BOUNDARY: THE PORTERS PASS–AMBERLEY FAULT ZONE AND 2010-12 CANTERBURY EARTHQUAKE SEQUENCE
Active blind structures starting to daylight from beneath the north Canterbury Plains indicate plate boundary deformation extends SE of the PPAFZ. Here the structural pattern of deformation is defined by NE trending thrust faults, expressed by growing asymmetric anticlines, blind to emerging thrusts and back-thrusts, that are regularly segmented by, and interact with, E-W trending dextral strike-slip faults overprinting and reactivating an inherited network of inclined Cretaceous to mid-Tertiary normal faults. This relay of structures is accommodating transpressional deformation in response to the regional WNW oriented maximum horizontal compressional stress.
The active late Quaternary deformation from the north Canterbury Plains when combined with the distribution and seismological characteristics of the 2010-2012 Canterbury Earthquake sequence provide important new insights into the structural evolution of these fault systems as they progress from lower strain peripheries into the more actively deforming parts of the NZ orogen. The structural mesh beneath the Canterbury Plains is analogous in both scale and geometry to the more evolved PPAFZ to the west.