Spatio-temporal hazard estimation in the Auckland Volcanic Field,New Zealand,with a new event-order model |
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Authors: | Mark S Bebbington Shane J Cronin |
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Institution: | (1) Volcanic Risk Solutions, Massey University, Private Bag 11222, Palmerston North, 4442, New Zealand;(2) Institute of Fundamental Sciences—Statistics, Massey University, Palmerston North, New Zealand |
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Abstract: | The Auckland Volcanic Field (AVF) with 49 eruptive centres in the last c. 250 ka presents many challenges to our understanding
of distributed volcanic field construction and evolution. We re-examine the age constraints within the AVF and perform a correlation
exercise matching the well-dated record of tephras from cores distributed throughout the field to the most likely source volcanoes,
using thickness and location information and a simple attenuation model. Combining this augmented age information with known
stratigraphic constraints, we produce a new age-order algorithm for the field, with errors incorporated using a Monte Carlo
procedure. Analysis of the new age model discounts earlier appreciations of spatio-temporal clustering in the AVF. Instead
the spatial and temporal aspects appear independent; hence the location of the last eruption provides no information about
the next location. The temporal hazard intensity in the field has been highly variable, with over 63% of its centres formed
in a high-intensity period between 40 and 20 ka. Another, smaller, high-intensity period may have occurred at the field onset,
while the latest event, at 504 ± 5 years B.P., erupted 50% of the entire field’s volume. This emphasises the lack of steady-state
behaviour that characterises the AVF, which may also be the case in longer-lived fields with a lower dating resolution. Spatial
hazard intensity in the AVF under the new age model shows a strong NE-SW structural control of volcanism that may reflect
deep-seated crustal or subduction zone processes and matches the orientation of the Taupo Volcanic Zone to the south. |
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