Application to Central South Island, New Zealand

Abstract

We apply our inversion methodology to 1-dimensional profiles in the central South Island of New Zealand which straddles the obliquely convergent boundary between the Australian and Pacific plates. The Alpine Fault is the largest fault in the region and accommodates the majority of this signal. The VDoHS and strain rates enable us to estimate fault parameters. Our findings are consistent with the Alpine Fault being a right lateral strike-slip fault with a small dip-slip component. The fault is dipping at ~60° with a hint of steepening to the south and is locked down to 10–21 km depth. To the north, we see evidence of deformation partitioning, consistent with transfer of much of the Alpine Fault motion onto the likely vertical and almost purely strike-slip Kelly branch of the Hope Fault. Estimates of the slip rate along the Alpine Fault leave up to 8–9 mm/year strike slip and ~5 mm/year horizontal convergence deficit from the total plate motion budget, likely taken up by zone of thrust faults 75–100 km to the southeast of the Alpine Fault.