Paul Tregoning: Crustal Deformation Studies

Paul Tregoning: Crustal Deformation Studies

Deformation-related Student Projects

Tectonic Hazards in Papua New Guinea


Linear velocities of GPS sites in PNG, showing absolute motions of the numerous tectonic plates

The Geodynamics Group has been involved in a major long-term project to measure and model present-day tectonic motion in Papua New Guinea since the first GPS surveys there in 1990. The program is run in cooperation with the National Mapping Bureau, the Papua New Guinea University of Technology, Lae and the Rabaul Volcano Observatory. The monitoring network spans almost the entire country with particular dense network across the South Bismarck/Pacific Plate boundary in New Ireland and east New Britain. The research brings together geodetic estimates of motion, seismic tomography and earthquake locations to understand more clearly the tectonic setting.

Current research is concentrating on:

  • identifying the deformation field between the South Bismarck and Pacific Plates
  • measuring the velocity field along the northern coastline of New Guinea and throughout the Highlands
  • monitoring deformation across the western end of the Bismarck Sea Seismic Lineation
  • understanding the rifting processes in the d'Entrecasteaux Islands and Papuan Peninsula

Selected relevant publications

Tregoning, P., M. Sambridge, H. McQueen, S. Toulmin and T. Nicholson, 2005. Tectonic interpretation of aftershock relocations in eastern Papua New Guinea using teleseismic data and the Arrival Pattern method, Geophys. J. Int., 160(3), 1103-1111.
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Tregoning, P. and A. Gorbatov, 2004. Evidence for active subduction at the New Guinea Trench, Geophys. Res. Lett., 31, doi:10.1029/2004GL020190.
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Tregoning, P., K. Lambeck, A. Stolz, P. Morgan, S. C. McClusky, P. van der Beek, H. McQueen, R. J. Jackson, R. P. Little, A. Laing, and B. Murphy, 1998. Estimation of current plate motions in Papua New Guinea from GPS observations J. Geophys, Res, 103, 12,181-12,203
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Atmospheric Pressure Effects


Peak-to-peak sub-daily vertical deformation from atmospheric pressure loading 		Atmospheric pressure loading causes an elastic deformation of the solid Earth. The magnitude of the effect can be up to 15-20 mm and it can vary by as much as 10 mm within a 24 hour period. As a result, this physical phenomenon affects the coordinates of geodetic sites (VLBI, GPS, SLR, DORIS etc) and should be accounted for in all high precision geodetic analyses. Periodic variations in pressure - or "atmospheric tides" - also cause surface deformation effects of up to a few mm and we are currently developing a new model for the atmospheric tides, including temporal variations in the amplitude and phase of the S1, S2 and S3 tides. Atmospheric pressure variations are also important in the reduction of GRACE (space-gravity) observations for estimating changes in the Earth's temporal gravity field. Local pressure variations must be applied at the observation level in GPS analysis when estimating accurate height variations.

Selected relevant publications

Tregoning, P. and T. A. Herring, 2006. Impact of a priori zenith hydrostatic delay errors on GPS estimates of station heights and zenith total delays, Geophys. Res. Lett., 33, doi:10.1029/2006GL027706.
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Tregoning, P. and T. van Dam, 2005. Atmospheric pressure loading corrections applied to GPS data at the observation level, Geophys. Res. Lett., 32, doi:10.1029/2005GL024104.
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Tregoning, P. and T. van Dam., 2005. The effects of atmospheric pressure loading and 7-parameter transformations on estimates of geocenter motion and station heights from space-geodetic observations, J. Geophys. Res., 110, doi:10.1029/2004JB003334.
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Present-day Glacial Isostatic Adjustment of Antarctica


Remote GPS installation at Landing Bluff, Antarctica 		Understanding present-day melting patterns of polar ice caps and the contribution to present-day sea level variations requires first unravelling the puzzle of how the continents are still adjusting after the melting that has occurred since the Last Glacial Maximum around 10,000 years ago.

The present-day glacial isostatic adjustment of Antarctica generates uplift of the continent that is detectable by space-geodetic observing techniques. The Gravity Recovery and Climate Experiment (GRACE) is sensitive to the induced gravity changes, while satellite altimetry and ground-based GPS can measure directly the vertical movement of the surface. These effects must be removed from GRACE and altimetry estimates of temporal changes in ice in order to estimate present-day mass balance changes that might be occurring as a result of global warming.

Since 1998, we have operated remote GPS installations in East Antarctica to measure the rate of uplift currently occurring as a result of ongoing glacial isostatic adjustment. Considerable care is required in the analysis of the GPS data to ensure that rates with an accuracy of < 1 mm/yr can be estimated.

Selected relevant publications

Tregoning, P., Welsh, A., McQueen, H. and Lambeck, K. 2000. The search for postglacial rebound near the Lambert Glacier, Antarctica . Earth Planets Space, 52 , 1037-1041.
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Tregoning, P., B. Twilley, M. Hendy and D. Zwartz, 1999. Monitoring isostatic rebound in Antarctica with the use of continuous remote GPS observations, GPS Solutions, 2, 70-75.
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