Crustal motions in Great Britain: evidence from continuous GPS, absolute gravity and Holocene sea level data

Abstract

S U M M A R YTwo independent continuous global positioning system (CGPS) processing strategies, based on a double-difference regional network and a globally transformed precise point positioning solution, provide horizontal and vertical crustal motion estimates for Great Britain. Absolute gravity and geological information from late Holocene sea level data further constrain the vertical motion estimates. For 40 CGPS stations we estimate station velocities and associated uncertainties using maximum likelihood estimation, assuming the presence of white and coloured noise. Horizontal station velocity estimates agree to <1 mm yr −1 between the two CGPS processing strategies and closely follow predicted plate motions. Residual velocities, generally <1 mm yr −1 , follow no regular pattern, that is, there is no discernible internal deformation, nor any dependence on station monumentation or time-series length. Vertical station velocity estimates for the two CGPS processing strategies agree to ∼1 mm yr −1 , but show an offset of ∼1 mm yr −1 with respect to the absolute gravity (AG) estimates. We attribute this offset to a bias related to known issues in current CGPS results and correct for it by AG-alignment of our CGPS estimates of vertical station velocity. Both CGPS estimates and AG-aligned CGPS estimates of present-day vertical crustal motions confirm the pattern of subsidence and uplift in Great Britain derived from Holocene sea level data for the last few thousand years: ongoing subsidence on Shetland, uplift in most areas of Scotland, and subsidence in large areas of England and Wales.

A continuous velocity field for Norway

“…They showed that the effect of including or not including an annual signal in the time-series analysis, is much larger when a power-law plus white noise model is used instead of a pure white noise model. Teferle et al (2009) argue that annual and semi-annual signals can bias the velocity In King et al (2010) theoretical vertical site velocity uncertainties for stations in the Northern Hemisphere of 1.41, 1.58 and 0.54 mm/year after 5 years of observations and 0.71, 0.79, 0.27 mm/year after 10 years of observations are derived using DD, Precise Point Positioning (PPP) and regional stacking, respectively. The uncertainties in the horizontal components are between a third and a fourth in the Double Difference (DD) solution and between half and a third in the Precise Point Positioning (PPP) solution.…”

“…We find differences between the different studies. Taking the uncertainties and transformation into account the differences between this study and Lidberg et al Differences between the different ITRFs have been discussed extensively in several papers (e.g., Argus 2007;Teferle et al 2009;Lidberg et al 2010;Altamimi et al 2011). In Norway the differences between ITRF2000 and ITRF2008, based on the transformation parameters , are approximately 1, 0 and 1 mm/year, in the north-, east-and height-component, respectively.…”

New Estimates of Present-Day Crustal/Land Motions in the British Isles Based on the BIGF Network

“…Furthermore, most of these stations have only been in-stalled since about 2004 and others have been frequently moved or shutdown. In view of this, only about 30 stations were considered suitable for geophysical applications in recent publications which considered data up to 31 December 2005 (Bradley et al, 2009;Teferle et al, 2009;Woodworth et al, 2009). Furthermore, these 30 stations provided a fairly inhomogeneous station distribution, with a lack of stations in the geophysically interesting areas of Scotland and Northern Ireland.…”

“…Furthermore, the inclusion of the CGPS stations in Northern Ireland, not available in Bradley et al (2009, defines the westerly boundary of the GIA-induced uplift over Scotland and Northern Ireland, which improves the geodetic constraints for future GIA models for the British Isles. derived from the vertical station velocities as obtained in ITRF2005 and from those in ITRF2005 then aligned to absolute gravity (AG) following Teferle et al (2009). In particular, this alignment is achieved by computing the weighted mean difference between the vertical station velocity estimates from CGPS and AG which is then subtracted from the CGPS estimates to form AG-aligned CGPS estimates of vertical crustal motions.…”

Ivestigating Glacial Isostatic Adjustement in Scotland with INSAR and GPS observation

“…Slight discrepancies exist regarding the location of maximum uplift within Scotland. While most CGPS solutions tend to place it in the eastern parts of Scotland [14,17], GIA modelling results and Holocene RSL data show it positioned in the west of the country [12,18]. …”