Abstract
At the southern part of the Taupo Rift, crustal extension is accommodated by a
combination of normal faults and dike intrusions, and the Tongariro Volcanic Centre
coexists with faults from the Ruapehu and Tongariro grabens. This close coexistence
and volcanic vent alignment parallel to the regional faults has always raised the
question of their possible interaction. Further, many periods of high fault slip-rate seem
to coincide with explosive volcanic eruptions. For some periods these coincidences are
shown to be unrelated; however, it remains important to evaluate the potential link
between them. In the Tongariro Graben, the geological extension was quantified and
compared to the total geodetic extension, showing that 78 to 95% of the extension was
accommodated by tectonic faults and only 5 to 22% by dike intrusions. Within the latter,
4 to 5% was accommodated by volcanic eruptions and 18 to 19% by arrested dike
intrusions, with an unknown percentage of hybrid extension. Short-term variations in
fault slip-rates and volcanic activity for the last 100 ka in the Tongariro Volcanic Centre
may have been influenced by static stress transfer between adjacent faults (within <20
km from the source) and dike intrusions (within <10 km), or by fluctuations in magma
input through time. The amount of magma involved in the rifting process will condition
the predominant extension mechanism and thus influence the predominant type of
volcano-tectonic interaction. A record of volcanic and seismic activity for the last 250 ka
was assembled, from new and published studies. This was used to analyse the spatiotemporal
associations between volcanic and seismic activity in the southern Taupo Rift.
Data on the faulting history, slip-rate variation and seismic hazard of the Upper Waikato
Stream, Wahianoa, Waihi and Poutu faults formed the core of the analysis. These
faults are capable of producing a MW 7.2 earthquake with a single-event displacement
of 2.9 m, posing an important hazard to the region. Data gathered in this study provides
an update to the National Seismic Hazard Model for New Zealand.
Date
2017
Rights
The Author
Publisher
Massey University
Description
Content removed from appendices for copyright reasons: Gómez-Vasconcelos, M. G., Villamor, P., Cronin, S. J., Procter, J., Kereszturi, G., Palmer, A., Townsend, D., … Ashraf, S. (2016). Earthquake history at the eastern boundary of the South Taupo Volcanic Zone, New Zealand. New Zealand Journal of Geology and Geophysics, 59(4), 522-543. doi: 10.1080/00288306.2016.1195757