The Te Puninga Fault, Hauraki Plains: a new seismic source in the low seismicity northern region of New Zealand

Abstract

ABSTRACT In this study, we provide the first field-based assessment of the seismic potential of the Te Puninga Fault, Hauraki Plains, Waikato region. Initially considered to be part of the nearby Kerepehi Fault, our new mapping and field data suggest the Te Puninga Fault is independent. A new net slip rate value of 0.25 mm/yr, based on geomorphic data and evaluations from two paleoseismic trenches, is slightly higher than previously considered. Comparisons of geomorphic expression between the two faults suggest that the slip rate currently assigned to the Kerepehi Fault could be underestimated. The earthquake magnitude estimated here for the Te Puninga Fault (Mw 6.9 ± 0.35) is based on a characteristic earthquake model. New PGA and MMI estimates here are only slightly larger than those published prior to this study. Although ruptures of the Te Puninga Fault are infrequent (derived recurrence range of 3000–11,500 years), and thus its hazard is low, with this paper we wish to enhance the community awareness to prepare for the rare large earthquake in the region. We also recommend that this new information is added to fault databases used for seismic assessment.