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Geographic coverage: The study focuses on the Mokonui Fault in the Wairarapa region, particularly near Masterton and surrounding rural areas. 

This report presents the findings of a paleoseismic investigation of the Mokonui Fault, an active fault located northwest of Masterton in the Wairarapa region. The fault is part of a group of splays from the Wairarapa Fault, which includes the Masterton and Carterton faults. The study was commissioned by the Wairarapa Engineering Lifelines Association to better understand the earthquake hazard posed by the Mokonui Fault. 
 
Researchers selected a site at Viewfield farm for trenching based on geomorphic features and the presence of swampy ground, which suggested the potential for preserved organic material suitable for radiocarbon dating. A trench was excavated across a fault scarp approximately 3.2 metres high. The trench revealed a complex stratigraphy of gravel, silt, peat, and organic layers, with multiple fault planes and a central fissure zone filled with peat. Radiocarbon dating of samples from the trench indicated at least two surface-rupturing earthquake events in the last 4,000 years, with a likely recurrence interval of 1,300 to 2,000 years. 
 
The style of faulting is interpreted as oblique, with both strike-slip and vertical components. The vertical component may be either normal or reverse, and the horizontal component is likely dextral. The estimated single event displacement is approximately 0.5 to 0.7 metres. The fault’s total slip rate is estimated at 0.3 to 0.7 mm/year. These values suggest the Mokonui Fault is capable of generating earthquakes of magnitude Mw 6.7 to 6.9. 
 
The findings are consistent with previous studies of the Masterton and Carterton faults, supporting the view that these faults share similar characteristics and pose comparable seismic hazards. The report recommends further trenching and dating to refine estimates of fault activity and improve hazard models for the region.