The kinematics of northern South Island, New Zealand, determined from geologic strain rates

Relative motions within the distributed plate boundary zone of northern South Island, New Zealand, are determined through an inversion of geologic strain rate estimates. The Quaternary fault slip rate estimates define the shear strain rates, and rock uplift rates provide information on the horizontal divergence rates. The major strike-slip structures within the Marlborough region are accommodating 80-100% of the total plate motion between Australia and Pacific plates on northern South Island; as much as 20% of the relative motion could be accommodated by shear generated by folding or thrust faulting with a single orientation between the major structures. Strain modeling indicates that the earthquake moment release over the last 150 years within the northwest Nelson province, which is west of the Marlborough region, is at least half an order of magnitude higher than the long-term rate of moment release. -from Authors