50thKaikoura05 -1- Kaikoura 2005 CHARACTERISATION OF NEW ...
50thKaikoura05 -1- Kaikoura 2005 CHARACTERISATION OF NEW ...
50thKaikoura05 -1- Kaikoura 2005 CHARACTERISATION OF NEW ...
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U-Th-Ra disequilibria data. In particular, it raises<br />
questions about the usefulness of geochronological<br />
interpretations of these data for andesitic volcanoes.<br />
The 1995 – 1996 eruptions of Ruapehu were the<br />
largest and best sampled events since the dome –<br />
forming eruptions of 1945. Nonetheless, the<br />
eruptions were small in global terms (< 0.02 km 3 )<br />
and entirely pyroclastic. Collectively, samples from<br />
the eruptions over the past 60 years display a<br />
spectrum of chemical compositions extending from<br />
andesite to dacite and covering much of the range<br />
shown by the prehistoric record, extending back<br />
150 ka. The temporal variations in isotopic and<br />
trace element variation for andesites and dacites<br />
erupted between 1945 and 1996 are systematic and,<br />
in comparison with prehistoric eruptives, they<br />
provide the basis of a model for predicting future<br />
eruption patterns. The model we have developed<br />
for the Ruapehu magmatic plumbing system could<br />
also be used to design seismic experiments that<br />
might be able to image magma storages beneath the<br />
volcano, thereby providing a more precise basis for<br />
predicting future eruptions.<br />
ORAL<br />
FORECASTING HAZARDS FROM MOUNT<br />
TARANAKI USING TITAN2D<br />
Jon Procter 1 , Shane Cronin 1 ,Abani Patra 2 ,<br />
Keith Dalbey 2 , Mike Sheridan 2<br />
&ThomasPlatz 1 ,<br />
1 Institute of Natural Resources, Massey University,<br />
Palmerston Nth, New Zealand<br />
2 GMFG, State University of New York at Buffalo,<br />
New York, USA<br />
(j.n.procter*massey.ac.nz)<br />
Over the last c. 800 years at Mt Taranaki at least<br />
nine distinct eruption episodes occurred, all of<br />
which involved lava dome production and collapse.<br />
Each episode produced several Block-and-Ash<br />
Flows (BAFs) that were directed north-westward<br />
out of a breached crater wall. The latest domecollapse<br />
in AD 1755 produced a deposit that<br />
covered an area of approximately 2.06x10 6 m 2 and<br />
reached up to 9.6 km from source. Future activity<br />
of this type could have a devastating effect on the<br />
Taranaki Region’s communities, infrastructure and<br />
economy. For hazard planning purposes, a<br />
Volcanic Hazard map of Taranaki was created in<br />
1996, with relative hazard zones relating to the<br />
frequency with which areas were inundated by<br />
volcanic flows in the past, with little consideration<br />
of present-day topography. If a similar sequence of<br />
events occurred today, what effect would current<br />
topography have on flow distribution?<br />
Additionally, would modelled flow inundation<br />
areas be similar to the mapped inundation zones<br />
based on past activity? A numerical geo mass-flow<br />
modelling approach is being used to answer these<br />
questions and to try constructing more-dynamic<br />
hazard maps that can take current topography into<br />
account. The Titan2D program (developed by the<br />
GMFG at SUNY Buffalo) is a “shallow water”,<br />
continuum solution-based, granular-flow model.<br />
The program is adapted by the user for various flow<br />
mechanical properties by changing values for<br />
internal and basal friction as well as the dimensions<br />
of the initial pile. Before this model can be applied<br />
to Taranaki BAFs, we must evaluate the input<br />
parameters. For this we use the AD 1755 casescenario,<br />
since initial collapse volume can be well<br />
constrained to the partially preserved summit dome.<br />
Internal and basal friction angles were evaluated<br />
through an iterative approach by broadly comparing<br />
modelled flow inundations with mapped AD 1755<br />
BAF deposit boundaries (especially run-out). A<br />
range of possible input parameters were determined<br />
to produce a suite of potentially inundated areas<br />
under present-day terrain. This suite of around 10<br />
forecasts from a uniformly distributed range was<br />
then analysed statistically to determine an overall<br />
map displaying relative probabilities of inundation<br />
by a future event of the same magnitude as AD<br />
1755. Using this constrained the range of input<br />
parameters, future hazard forecasts for this scale<br />
and type of event can be undertaken using the<br />
present summit configuration, and altered to<br />
include any changes to topography in the future.<br />
This type of approach may also be adapted to<br />
developing appropriate models for other types and<br />
scales of mass flows possible on Mt Taranaki.<br />
Using this approach with outputs representing<br />
differing probabilities for each event modelled what<br />
methods can be applied to effectively and<br />
efficiently display the hazard and associated risk.<br />
ORAL<br />
PROGRESS REPORT: PALEOMAGNETIC<br />
ANALYSES <strong>OF</strong> KASTEN CORES FROM THE<br />
WAIPAOA BASIN, <strong>NEW</strong> ZEALAND<br />
A. Quinn,J.Robbins&G.Wilson<br />
Geology Department, University of Otago, PO Box<br />
56, Dunedin.<br />
(quial125*student.otago.ac.nz)<br />
U-channel samples were collected from several<br />
kasten cores in January <strong>2005</strong> from a research cruise<br />
(KM0502) as part of the Margins Source to Sink<br />
research programme in the Waipaoa Basin, New<br />
Zealand<br />
(http://www.margins.wustl.edu/S2S/S2S.html).<br />
Magnetic measurements of NRM intensity and<br />
direction, magnetic susceptibility (�) and<br />
treatments of AF demagnetisation, ARM and IRM<br />
have been performed. The results from these<br />
measurements are being used in studies to<br />
50 th <strong>Kaikoura</strong>05 -71- <strong>Kaikoura</strong> <strong>2005</strong>