Dike intrusion and displacement accumulation at the intersection of the Okataina Volcanic Centre and Paeroa Fault zone, Taupo Rift, New Zealand

Abstract

We examine the relationship between dike emplacement and normal fault displacement along the south-western margin of Okataina Volcanic Centre, New Zealand. At this location dikes (including a basaltic dike up to 5 m wide at the ground surface intruded during the 1886 AD Tarawera eruption) formed over the last 22 kyr in the Tarawera linear vent zone within a few kilometres of the Paeroa Fault zone. Displacement analysis and mapping of fault scarps indicate that fault and dike extension are complementary over time periods of tens of thousands of years. Extension that is primarily accommodated by faulting outside the volcanic complex is achieved by dike intrusion and faulting within it. Historical observations following the 1886 AD eruption and previously published active fault trenching collectively indicate, however, that dike intrusion generally does not induce slip within the Paeroa Fault zone close to the lateral dike tip. We suggest that displacement in the Paeroa Fault zone outside the Okataina Volcanic Centre is generally not triggered by eruptions and that this fault is principally tectonic in origin.