Deformation at Taupo volcano, New

Zealand, measured by InSAR, lake

levelling and GPS

Jessica K. Hole(1,2), Bradley J. Scott(3), John Beavan(3),

Geoff Wadge(2) and Nicki Stevens(4)

(1) NPA Group, UK, Email: jessica.hole@npagroup.com

(2) Environmental Systems Science Centre, UK

(3) GNS Science, New Zealand

(4) Ministry for the Environment, New Zealand

FRINGE 2007

Outline

• Background to Taupo Volcano

• Contemporary deformation

• Available data

– InSAR

– Campaign and continuous GPS

– Lake levelling

• Comparisons between datasets

• Conclusions

Taupo Volcanic Zone

• High heat flow

~4200 W

• Segmented

volcanism

• 9 Caldera systems

• Okataina and

Taupo are

considered active

today

• Extension

~8-15 mm/year

Ngaurahoe

Andesitic

Andesitic

Rhyolitic

Taupo volcano

• Multiple rhyoliticeruptions

• 26.5 ka Oruanui

– Magnitude 8 eruption

– 530 km! of magma

• 186 CE Taupo

– Magnitude 7 eruption

– Most recent calderaforming eruption

– Extremely violent

• Located on TaupoFault Belt

186 CE

26 .5 ka

Wairakei-Tauhara

Geothermal Field

Taupo Fault Belt

Contemporary deformation - 1

• 3 major episodes of shallowtectonic seismicity duringthe last century

• 1922– ~4m uplift

• 1965

• 1983– Pre-Seismic deformation:

Uplift of ~35 mm

– Co-Seismic deformation:Normal fault offset on theKaiapo fault of ~50 mm

– Post-Seismic deformation:Continued subsidence for 4-5months

Contemporary deformation –

2

Three distinct deformation periods

Motivation

• Hazard monitoring

• Identification of different deformation sources

• Better understand the interactions betweentectonics and volcanism

What is the best way to measure the

deformation and separate the

different sources?

Data sources

InSAR

• 24 Ascending IS2

images

• 21 Descending IS5

images

• Temporal

decorrelation

• Velocity and time-

series analysis

using the IPTA

technique

140 days

IPTA - ascending

A

B

4.7 ± 1.1 mm/yr-10.9 ± 1.3 mm/yr

B - Acacia BayA - Kinloch

IPTA - descending

A

B

-0.5 ± 1.4 mm/yr-5.3 ± 1.4 mm/yr

B - Acacia BayA - Kinloch

Campaign GPS

Campaign GPS

• 1992-2005

• 120 stations in TVZ

• Uneven occupationhistory

• No vertical motioncomponent

Campaign GPS

Continuous GPS

• One station with more

than 2.5 years of data

• Motion relative to

Auckland outside TVZ

• Full motion vector is

available

Lake levelling

• 23 stations in total

• 2-4 times a year

Lake levelling

West East

5 km

GPS vs lake levelling

Levelling - Motion of Taupo relative to Kinloch

CGPS – Motion of Taupo relative to Auckland

InSAR vs lake levelling

Motion of Taupo

relative to Kinloch

Conclusions

• Uplift from west to east across the north of the lake

with the maximum uplift focussed near Acacia Bay

• Magmatic centre is rising, superimposed on wider

tectonic extension

• InSAR has been shown to be complementary to

other geodetic techniques, particularly those that are

more sensitive to horizontal motion, allowing a fuller

picture of vertical deformation to be established.

• Shallow source most probably related to

hydrothermal pressure driven by hot magma at depth