Cooperative Institute for Research in Environmental Sciences

New Zealand - Southern Alps

New Zealand GPS

Supported by NSF’s Instruments and Facilities and Theoretical and Experimental Geophysics Programs

Collaborators (recent past and present)

• John Beavan and Deion Matheson, Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand
• Paul Denys and Mike Denham, Department of Surveying, Otago University, Dunedin, New Zealand
• Brad Hager and Tom Herring, Department of Earth, Atmospheric, and Planetary Sciences, MIT

In early 2000 we installed a GPS network consisting partly of continuously recording receivers and temporary receivers that recorded 3-6 months during the austral summer (Figure 1). Our goal has been to measure accurately vertical movement across the Southern Alps, a region where rock rises especially rapidly with respect to sea level largely in response to the very rapid erosion of the western flank of the Southern Alps. Results [Beavan et al. 2004, 2010] show that the vertical component of movement increases from a low value on the west coast to a maximum of about 5 mm/yr between ~10 and 30 km from the Alpine fault, which bounds the Southern Alps on its western flank, and then decreases eastward again.

Figure 3. Relative vertical velocity profile across the Southern Alps from the west coast to the eastern foothills.  Lines show predictions of interseismic vertical rate from elastic dislocation models (green) using two different coupling distributions on the 45°-dipping Alpine Fault [Wallace et al., 2007; Beavan et al., 2007]  and from numerical models with more prescribed rheological and temperature structures (black) [Ellis et al., 2006].. In dislocation models the SE block boundary dips ~60° NW, with a coupling factor of 0.9-1 to 25 km depth and zero below. Solid grey line shows smoothed topography along the transect.

References

Beavan, J., P. Denys, M. Denham, B. Hager, T. Herring, and P. Molnar (2010), Distribution of present-day vertical deformation across the Southern Alps, New Zealand, from 10 years of GPS data, Geophys. Res. Lett., 37, L16305, doi:10.1029/2010GL044165.

Beavan, J., D. Matheson, P. Denys, M. Denham, T. Herring, B. Hager, and P. Molnar (2004), A vertical deformation profile across the Southern Alps, New Zealand, from 3.5 years of continuous GPS data, Proceedings of the Workshop: The state of GPS vertical positioning precision: Separation of earth processes by space geodesy, ed. by T. van Dam and O. Francis, Cahiers de Centre Européen de Géodynamique et Séismologie, vol. 23, Luxembourg, 111-123.