Reassessment of slip rate and implications for surface rupture hazard of the Martinborough Fault, South Wairarapa, New Zealand

New mapping of the Martinborough Fault utilising high resolution LIDAR data and orthophotos defines a c. 1.3 krn long active fold trace consisting of a broad (50-150 rn wide) warp crossing dissected alluvial fans. GPS survey profiles across the fold-scarp reveal vertical separations ranging from 1.2 to 6 m on two fan surfaces. Published OSL ages imply a Porewan age for the upper fan (surface age c. 55 ka). We calculate a revised vertical slip rate of c. 0. 1 mm/yr (previously published rates range between 0.3 and 0.67 mrn/yr) and a recurrence interval of c. 15 000 yr from these new data. This places the fault within the Ministry for the Environment Active Fault Guidelines Recurrence Interval Class V (>10 000 to >= 20 000 yr), to which a medium level of confidence is assigned.