New Zealand Journal of Geology and Geophysics abstracts

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Vertical deformation and shallow seismicity around Lake Taupo, New Zealand, 1985-90

PETER M. OTWAY
STEVEN SHERBURN

Institute of Geological and Nuclear Sciences Ltd
Wairakei Research Centre
Private Bag 2000
Taupo, New Zealand

Abstract  Vertical deformation and shallow seismicity around Lake Taupo, which occupies much of the Taupo Volcanic Centre, displayed two regionally distinct patterns during the 1985-90 study period. In the Taupo Fault Belt, north of the lake, there was aseismic sag. A high rate of relative subsidence of 10 +/- 1 mm/yr resulted in inward tilt exceeding 1.0 +/- 0.1 urad/yr, but was accompanied by almost no seismic activity. In contrast, the lakeshore and islands within the central and southern part of the lake displayed repeated small oscillations in height, superimposed on a pattern of slow tilt to the southwest, while the seismicity of this area was characterised by frequent small earthquake sequences. Four periods were identified when rates of deformation and seismicity within the southern area appeared to increase above previous levels, but there was no evidence of a one-to-one correspondence between deformation and individual seismic events. Both phenomena are thought more likely to reflect responses, at different time scales and depths, tothe underlying strain release.

Keywords  vertical deformation; seismicity; Lake Taupo; Taupo Fault Belt; Taupo Volcanic Centre; Taupo Volcanic Zone; volcanism; caldera unrest; lake level monitoring

PDF file of entire paper: medium quality (530K); (scanned from paper original: notes about this process)

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