|Bateson, L, and Novellino, A. 2018. Glasgow Geothermal Energy Research Field Site - Ground motion survey report. British Geological Survey Internal Report, OR/18/054.|
Collection, interpretation and processing of geo-thematic data were fundamental to characterise the spatial and temporal evolution of ground stability conditions from 1995 to 2017 in and around the GGERFS site. For the GGERFS site and wider Glasgow area ground motion data has been examined for three periods using three processing techniques. The following is evident from the data:
- Glasgow and the surrounding area is largely stable for the time periods 1995–2001, 2002–2010 and 2015–2017
- We found no evidence for ground motions relating to the coal mining history of this area. We do not see the regional patterns of uplift that has been observed in InSAR results for other UK former coal mining areas likely due to the age of mining, which stopped in the late 19th and early 20th century in urban parts of Glasgow. Investigation of the InSAR time
- series for media reported subsidence events in Glasgow show that fast motions involving a small spatial area are difficult to detect with InSAR.
- Small areas of ground motion are observed; these are interpreted to be caused by the compression of natural superficial deposits and man-made ground. This is especially true where there has been recent anthropogenic activity such as building or quarrying. Subsidence and uplift relating to volume change within superficial peat deposits are also observed and some cyclicity is evident within the motion time series for these points, which may relate to changes in water content.
- A constant, yet small, pattern of subsidence is observed along the Clyde in the TRE ALTAMIRA data, this corresponds to compression of the alluvial deposits.
- The GGERFS site has a lack of radar reflectors in the 1990’s and 2000’s due to the lack of buildings/radar reflectors at that time. In 2015–2017 radar targets are introduced by the development which has taken place. Although not a dense network of points they do reveal small rates of subsidence which appears to have started in early 2016. This subsidence likely relates to settling of the relatively thick superficial and man-made deposits within the area.
- Similarly, settlement of the Commonwealth Games Athletes village housing area to the west of Cuningar Loop is observed in the 2015–2017 data.
- The three types of InSAR processing applied to the site provide comparable results; we see the same features in the average velocity plots for SqueeSAR™ and ISBAS.
- As expected the ISBAS Sentinel-1 processing provides almost complete coverage for the average linear velocity results, however, due to the lower spatial resolution and lack of time series it is harder to use this data to fully understand the motion characteristics
Now that we have characterised the ground motions in the Glasgow area for the last three decades we have a good baseline on which to monitor any potential effects of the planned geothermal research activities. Further InSAR investigations with the Sentinel-1 constellation are planned to be conducted once the abstraction and re-injection of mine water activities start in order to analyse any disturbance derived by human activities to the preceding natural condition described in this report.
The next investigation of ground motion conditions for GGERFS will account for additional information coming from both passive and active radar reflectors planned to be installed at Cuningar Loop in late 2019. These will be used to calibrate SAR imagery and will guarantee reliable InSAR measuring targets.