OR/17/049 Ground deformation

Ward, R S1, Smedley, P L1, Allen, G2, Baptie, B J1, Daraktchieva, Z3, Horleston, A7, Jones, D G1, Jordan, C J1, Lewis, A4, Lowry, D5, Purvis, R M4, and Rivett, M O6. 2014. Environmental baseline monitoring project: phase II - final report. British Geological Survey Internal Report, OR/17/049. (1) British Geological Survey, (2) University of Manchester, (3) Public Health England, (4) University of York (National Centres for Atmospheric Science), (5) Royal Holloway University of London, (6) University of Birmingham, (7) University of Bristol

Introduction

There is speculation whether there is any potential for shale gas operations at depth to cause surface ground deformation. Conventional oil and gas operations have on rare occasions been shown to result in subsidence above compacting oil and gas reserves (Geertsma, 1973) and a recent study suggests that surface uplift in eastern Texas was due to fluid injection, which was distinguished using satellite remote sensing (Shirzaei et al., 2016). These studies do not imply that shale gas operations at depth will cause ground motion. Nevertheless, undertaking objective and authoritative monitoring of the ground surface at operation sites and surrounding regions is advisable (a) to determine if there are any impacts on the ground surface and (b) to reassure the public that appropriate independent monitoring of all potential environmental impacts is being undertaken. Knowledge regarding the baseline ground motion conditions, compared with the current situation, would enable the provision of impartial and objective information on whether shale gas operations have affected the status of the landscape.

The key monitoring question is whether shale gas operations are altering the earth surface processes that are operating at the site. We cannot assume that an area is stable prior to shale gas operations. When considering a monitoring system, it is important to account for the dynamic nature of the earth’s surface i.e. there may be some pre-existing displacement due to either natural or induced factors. Therefore, a baseline survey is required to determine the pre-existing conditions of the site including displacement such as upwards motion (uplift), downwards motion (subsidence) or horizontal/lateral motion, and ongoing monitoring during any operations is required to characterise the current situation.

The investigation in this work package is designed to monitor the surface ground motion (subsidence, uplift or stability) of the target area using line of slight (LOS) interferometric synthetic aperture radar (InSAR) from orbiting satellites prior to any permitted unconventional gas production in the Vale of Pickering. InSAR is considered an appropriate technique for ground motion monitoring because

1. archive radar data (acquired by satellites since 1992) are available and can be utilised to ascertain a baseline of motion (or lack of motion) prior to any permitted gas operations
2. data from currently-orbiting satellites such as Sentinel-1A can be analysed to acquire information about the ongoing surface ground motion conditions in a region
3. the analysis produces data over a region rather than at a point location, which other techniques such as GNSS provide

Table 18 provides a guide to the advantages and limitations of remote and in situ systems for ground motion monitoring.

Table 18    Comparison of remote and in situ ground surface motion monitoring systems.

Monitoring technique	Advantages	Limitations
InSAR	Measurements are made remotely (non-invasive) Measurements can be made using historic data to gain a baseline prior to operations. Imagery can cover a large area simultaneously. Entire deformation field can be imaged, rather than isolated points.	Conventional techniques have difficulty in vegetated areas. High magnitudes of motion (greater than the satellite detected phase difference) cannot be measured. Temporal and spatial resolution is limited by satellite set up and orbital parameters. Affected by steep topography (shown not be an issue in most of the UK).
GNSS	High precision. Does not require line of sight between benchmarks. Continuous site can operate without frequent human interaction.	Equipment can be stolen/vandalised/damaged. Sampling of deformation field is limited to individual points; several points are required. Requires at least 4 satellites in view simultaneously.
Tiltmeters	High precision. Does not require line of sight between benchmarks. Continuous site can operate without frequent human interaction.	Equipment can be stolen/vandalised/damaged. Sampling of deformation field is limited to individual points. Complex installation (e.g. in boreholes) — several tiltmeters are required.
Total Stations	High precision. Continuous sites can operate without frequent human interaction.	Requires line of sight between benchmarks. Generally they are operated manually, requiring repeat site visits to operate the system.

To date, the InSAR process has not been applied to monitoring energy operations in the UK because of the challenge of gaining coherence over non-urban areas. To resolve this challenge, we processed the data using the conventional SBAS (small baseline subset) process to gain precise results over urban areas and subsequently utilised the ISBAS (intermittent small baseline subset) process to acquire results over the non-urban areas.

BGS has experience of applying InSAR to several ground surface monitoring applications in the UK e.g. utilising 55 ERS-1/2 images between 1992 and 1999 to investigate ground motion linked to ceased mining operations in south Wales (Bateson et al 2015). The InSAR technique was subsequently applied as part of the BGS-funded project to monitor environmental baseline conditions in Lancashire where planning applications were submitted by Cuadrilla in 2014 for the development of shale gas, see www.bgs.ac.uk/research/groundwater/shaleGas/monitoring/lancashire.html.

The deliverable in this ground motion work package is to provide ‘an analysis of satellite (InSAR) data’. In order to achieve this, the following steps were followed:

• Obtain stacks of satellite SAR data
• Process the data using the SBAS InSAR techniques (thereby deriving results primarily for urban areas)
• Process the data to ISBAS level, thereby extending the results to non-urban areas)
• Provide an analysis of the InSAR results.

The work package utilised the ISBAS technique of InSAR analysis as it has been found to provide results in non-urban areas where other InSAR techniques fail. The conventional SBAS technique requires that the target shows coherence in every image of the stack, while the ISBAS technique utilises coherence that is intermittent throughout the stack. Both SBAS and ISBAS processing and analysis was undertaken on each stack of radar images to provide results in urban and non-urban areas.

Data selection

Three sets (stacks) of satellite radar data were acquired for the Vale of Pickering (Table 19). Archive radar data were acquired by the ERS-1/2 and ENVISAT satellites for the periods 27th May 1992–30th December 2000 and 13th July 2002–21st February 2009 respectively. Data were also acquired from the Sentinel-1 satellite covering the period 8th May 2015 to 30th August 2016. Sentinel-1 is continuously orbiting and collecting data, however imagery after August 2016 were not included in this study due to time limitations for processing and interpretation. There is no satellite coverage in the region between 2009 and 2014 due to the orbital decay of ENVISAT. No alternative commercial data are available to this study due to lack of acquisition in this time period. Nonetheless, we consider the period 1992–2009 is sufficient to provide a meaningful baseline assessment of ground motion prior to unconventional gas operations. The three stacks of data were analysed using SBAS and ISBAS InSAR techniques, i.e. six sets of analysis were undertaken and completed within this ground motion work package.

Table 19    InSAR data and processing levels for the Vale of Pickering.

Satellite	Time period	No. of scenes in the stack	Processing mode	Max velocity (mm/yr)	Min velocity (mm/yr)
ERS-1/2	1992–2000	72	SBAS	+3.3	-3.1
ERS-1/2	1992–2000	72	ISBAS	+6.2	-4.4
ENVISAT	2002–2009	25	SBAS	+5.8	-4.4
ENVISAT	2002–2009	25	ISBAS	+9.3	-7.3
Sentinel-1A	2015–2016	36	ISBAS	+18.4	-11.8

Ancillary data

A selection of ancillary datasets (listed below) were obtained in order to undertake the interpretation process:

1. Bedrock geology (incl. faults)
2. Surficial geology (incl. compressible ground)
3. Historic mining information/plans
4. Seismic records
5. Groundwater abstraction records
6. Borehole records
7. Geohazard information (e.g. landslides and shrink/swell)
8. Landcover information
9. Historic topographic maps
10. Aerial photography
11. Digital elevation models
12. Digital terrain models

Data processing activities

Our approach to acquiring, processing and interpreting the InSAR data is briefly outlined in this section. The methodology to effectively undertake the monitoring programme of ground motion conditions using InSAR techniques is illustrated in Figure 132 with the associated actions listed below. These describe monitoring of both the archive and continuous (‘current’) ground motion conditions:

1. Search of catalogue satellite radar data to confirm that suitable stacks of images were available for the study area.
2. Download the stack of image datasets covering the geographic area and the time period(s) of interest.
3. Process the imagery for the region using SBAS and ISBAS InSAR technique(s).
4. Ensure that the outputs from the InSAR processing match the quality required e.g.

Suitable density of spatial coverage in the area of interest

Suitable temporal coverage in the area of interest

Assess output statistics to gauge if the results are fit-for-purpose

5. Interpretation of the InSAR outputs. This is a key stage because the outputs from the InSAR image processing are dependent on the quality of the interpretation. There are two fundamental components.

Ensure that interpretation is undertaken by sufficiently-experienced personnel. For shale gas applications the interpretation should be done by experienced geoscientists who compile and integrate a suite of geoscientific information (noted below)

The interpretation was reliant upon access to a comprehensive range of ancillary data, listed in the section above

The ERS and ENVISAT scenes were multi-looked by a factor of 4 × 20 (range × azimuth) while Sentinel-1 by 5 × 22 in order to obtain pixel sizes of 0.01 km² and 0.008 km², respectively. A threshold of 250 m and 4 years was applied to generate 502 ERS and 62 ENVISAT interferograms to minimise the presence of temporal and spatial phase decorrelation components in the interferograms and enhance phase quality of the processed pixels (and hence the coherence). The shorter revisit time (12-days) and the narrow orbital tube provided by Sentinel-1 acquisitions, enabled the production of a higher number of interferograms (589) by employing a perpendicular baseline of 200 m and a temporal baseline of one year (Figure 133). The Initial topographic information for the processing area was extracted from the 90 m resolution Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) made available by NASA (Farr et al., 2007). The reference point locations, to which ground motion estimates refer, were set in York [53.96 N, -1.08 E] and Scarborough [54.280536 N,–0.405730 E]. These areas have been chosen because of the high interferometric coherence across all small baseline interferograms and also because they should be less susceptible to ground motion hazards identified in the BGS GeoSure dataset (Walsby, 2008).

Figure 132    Flowchart of the approach and data utilised for the ground motion InSAR monitoring work package.

Figure 133    The perpendicular orbital baseline (Bperp) plotted against the relative time (temporal baseline) of each ERS, ENVISAT and Sentinel-1 image relative to its master corresponding to the black dot. The ERS master is 25th January 1997, ENVISAT master is 8th May 2004 and Sentinel-1A master is 24th August 2015.

The ISBAS technique of InSAR analysis was employed as it has been found to provide results in non-urban areas where other InSAR techniques fail. Figure 134 illustrates the importance in the Vale of York of an InSAR technique that will work outside urban areas, with most of the land cover classified as non-irrigated arable land. The conventional SBAS technique requires that the target shows coherence in every image of the stack (Berardino et al., 2002), while the ISBAS technique utilises coherence that is intermittent throughout the stack. To select the most suitable pixels for the time-series analysis and for the calculation of the LOS velocity of each, a coherence threshold of 0.25 in at least 150 ERS, 30 ENVISAT and 170 Sentinel-1A interferograms was chosen. These were found to obtain the best results over both urban and non-urban areas for each of the stacks.

Figure 134    Ground Coverage of ERS, ENVISAT and Sentinel-1A frames used for the Vale of Pickering overlaid onto the Sentinel-1A detected backscattered intensity (a). CLC2012 land cover for the area of interest (b). Extension of each land cover class for Vale of Pickering from CLC2012 (c).

Results of vale of pickering insar analysis

The processing of the InSAR data has provided the first baseline assessment of land surface deformation covering a 25-year period in the Vale of Pickering, albeit with a gap in the coverage following the ENVISAT de-orbit and prior to Sentinel-1 launch. The results from the SBAS analysis comprises 47 930 ERS, 72 697 ENVISAT and 71 881 Sentinel-1A points which increase to 836 939 ERS, 234 793 ENVISAT and 637 753 Sentinel-1A points in the ISBAS results (Figure 135).

Figure 135    ERS SBAS (a), ERS ISBAS (b) ENVISAT SBAS (c), ENVISAT ISBAS (d), Sentinel-1A SBAS (e) and Sentinel-1A ISBAS (f) results for the Vale of Pickering area, showing average rates of ground motion for ISBAS points. Location of GNSS stations and reference point are indicated with a black triangle and star, respectively.

Archive radar satellite data from 1992–2000

75 ERS-1/2 SAR scenes for 1992–2000 are available along satellite track 366 in descending mode. Of the 75 ERS-1/2 scenes in the archive, three were not used due to missing lines within the data. The results of the ERS-1/2 InSAR analysis are shown in Figure 136. Green areas are considered stable, red are subsiding on average over the time period, and blue are undergoing uplift.

Figure 136    InSAR SBAS (top) and ISBAS (bottom) analysis of ERS-1/2 satellite imagery (1992–2000) for the Vale of Pickering. Radar data supplied to BGS by ESA under grant id.31573. Contains Ordnance Data © Crown Copyright and database rights 2017.

As expected, the SBAS results are primarily constrained to urban areas (including roads) as these provided coherence in all of the radar images in the stack. It is apparent that the analysis shows that the area was predominantly stable between 1992 and 2000. There does appear to be a discrete zone of subsidence north of Whitby (in the Loftus area) but this is outside the Vale of Pickering monitoring area.

The ISBAS analysis of the ERS-1/2 radar also data indicates that the majority of the area was stable. There are three zones of ‘dispersed’ uplift in this analysis, to the west, southwest and south of Scarborough. We believe that these zones in the ISBAS analysis are not related to geological motion (in our experience geological motions are more discrete), but are most likely due to vegetation changes and agricultural practices.

Archive radar satellite data from 2002–2009

25 ENVISAT scenes for 2002–2009 along satellite track 366 in descending mode were ordered from ESA. 24 of the available 25 radar images were utilised; the scene acquired on 8th January 2005 was excluded due to failure to meet the baseline criteria. The relatively low number of scenes in the ENVISAT stack is a data limitation, and may have resulted in reduced compensation for some atmospheric effects. The results indicate a maximum velocity of 9.3 mm/year. The SBAS InSAR analysis comprises 72 697 points while the ISBAS analysis comprises 234 793 points (Figure 137).

As with the 1992–2000 InSAR analysis, the SBAS results suggest that the urban areas are not affected by widespread subsidence or uplift, i.e. they are predominantly stable. There are some zones of dispersed uplift, notably along the coast southwards from Scarborough, and in the central and western extremes of the Vale of Pickering. The dispersed nature of the uplift could suggest that they are not due to geological motion, but could be due to atmospheric effects however validation against GNSS data and the uplift visible in the higher measurement density Sentinel-1 data suggest that the uplift is geological in nature. The interpretation of the GNSS and Sentinel-1 data are described in future sections of the report.

The ISBAS analysis corroborates the SBAS analysis and provides additional results across the region. The ISBAS analysis identifies a discrete zone of subsidence to the south of the Vale of Pickering monitoring area and adjoining its southern boundary. This correlates with an area of compressible ground in the BGS GeoSure product, and we believe that this is genuine surface ground motion.

Within the Vale of Pickering ISBAS analysis there are significant zones of dispersed uplift. These do not seem to show any correlation with the zones of dispersed uplift in the ERS-1/2 ISBAS analysis, nor do they correlate with bedrock, superficial geology or compressible ground databases. Their dispersed nature suggests that they are not the result of geological motion. Due to the relatively small number of scenes in the stack they could be the result of atmospheric effects.

Ongoing monitoring using current satellite radar data (2015 onwards)

Imagery acquired by the ESA Sentinel-1A satellite between 8th May 2015 to 30th August 2016) was acquired and processed. The stack comprised 36 images. SBAS processing of the Sentinel-1A data resulted in an average point density of ∼17 SBAS points/km². When the Sentinel-1A data was processed with ISBAS the number of points increased by a factor of ∼8.3, providing a coverage of 89% (corresponding to ∼141 points/km²) with the highest increase in measurement density observed in areas of non-irrigated arable land, pastures and natural grasslands (Figure 138). The additional coverage has not come at the sacrifice of quality with an average standard error of 1.93 mm/year. As expected, the coherent targets concentrate over the urban areas of Scarborough, Pickering and Malton where the highest values of the interferometric coherence were observed.

The network of GNSS receiving stations from the NERC British Isles continuous GNSS facility (available at www.bigf.ac.uk) was used to validate the ISBAS time-series over two sites (Figure 135). The SCAR station (from 05/01/03 to 09/02/09) renamed to SCAO (from 20/02/09) and the YEAR station (from 24/05/04–22/01/09) then renamed to YEAS (from 16/04/09 to 10/03/16) time-series GNSS data were used to validate/constrain the magnitude and timing of ENVISAT and Sentinel-1A motion (Figure 139).

Figure 137    InSAR SBAS (top) and ISBAS (bottom) analysis of ENVISAT satellite imagery (2002–2009) for the Vale of Pickering. Contains Ordnance Data © Crown Copyright and database rights 2017.

Figure 138    Average SBAS and ISBAS densities obtained for each land cover type from ERS, ENVISAT and Sentinel-1 results (CLC2012).

Figure 139     Non-linear time series for selected ISBAS points. The solid lines represent the ISBAS non-linear vertical displacements for the different acquisitions and the dotted lines represent the GNSS linear and vertical displacements which were derived separately. It is worth noting that the InSAR time series reported were generated considering a linear displacement velocity in the temporal gaps between the ENVISAT and Sentinel-1A datasets.

The displacements at the two GNSS stations, at rates of -0.54 mm/yr for SCAO-SCAR and -0.56 mm/yr for YEAR-YEAS, are in agreement with the subsidence observed at the closest ISBAS points for the equivalent time span, confirming the validity of the InSAR results.

Figure 140 illustrates the average annual ground motion derived from ISBAS results for the Pickering-Malton area. An area of uplift (of ~5 mm/yr) is visible in the western sector of the valley, between Pickering and Malton, for the 2002–2009 time-span which almost doubles (to ~10 mm/yr) for the 2014–2016 period and has been detected through intermittently coherent targets. The uplift is delimited both to the north and south to the presence of Quaternary lacustrine deposits of the Glacial Lake Pickering (Evans et al., 2016). There also appears some correspondence between uplift and east-west faults, identified as dashed lines in Figure 140. The fault lines depicted on the geological maps at this scale represent only approximate locations of the faults at the surface. The geometry of faults, e.g. their dip, is also complex, and so further analysis is required to better understand the cause(s) and controls on the observed uplift.

Figure 140    ISBAS InSAR results for the Pickering area of the Vale of York. Blue areas are undergoing uplift while green/yellow areas are stable. Dashed lines are geological faults. Solid black line is the trace of the section in Figure 139. Contains Ordnance Data © Crown Copyright and database rights 2017.

The spatial pattern of the Sentinel-1 ISBAS velocities reveals the occurrence of instability within the clay and silt sediments of the lacustrine deposit which south of Kirby Misperton exceeds 20 m in thickness (Figure 10). Faults of the basement play a significant role in the heterogeneity of the uplift rates by identifying three main domains:

1. the northern one with average velocities ≥6 mm/yr;
2. the central section with velocities ≤3 mm/yr;
3. southern portion with velocities ~5 mm/yr.

Abrupt changes in the ground motion at the location of a fault (Figure 141) suggesting that the faults constrain the motion, possibly by their influence on the ground water flow at depth.

Figure 141    ISBAS InSAR results for the Pickering are of the Vale of York across the section identified in Figure 9.

Figure 142    Bedrock geology and faults for the Pickering area of the Vale of York. Brown areas are clays from the quaternary glacial lake, green represents Chalk whilst the yellows and pinks to the North and South are the Coralline limestones and Calcareous Grits.

Considering the uniform rates of uplift in the InSAR time series, a possible source of the observed uplift might be the natural groundwater recovery in the gas reservoirs of North Yorkshire, namely the Permian Kirkham Abbey Formation (BGS, 2000). The top of the Kirkham Abbey Formation is at 1000/1200 m depth and it is postulated that following the decline in gas production as the reservoir depleted, a pressure gradient has been set up which has drawn in the surrounding groundwater. This groundwater has then increased the pore pressure and hence led to surface uplift.

Other possible explanations for this uplift relate to the wet winter of 2015–2016, the Corralline Limestone to the North and South of the Vale of Pickering (Figure 11) may allow a groundwater flow, which recharges the aquifer at depth, thereby increasing the pressure. Alternatively, the uplift may relate to shallower processes; the increase in surface water (many members of the public at the engagement events suggested there was a great deal of surface flooding during the winter of 2015–16) may have led to a swelling of the glacio-lacustrine clays Figure 11), which are responsible for the flat topography of the Vale. The InSAR time series supports the notion that the uplift relates to the timing of a wet winter as we see an increase in uplift rates following the winter of 2015–2016 (Figure 143).

Figure 143    ISBAS InSAR Time series for the Pickering (green) and Malton (blue) areas.

Problems/issues encountered and explanation of cause(s)

There were no significant issues encountered. The ENVISAT, ERS-1/2 and Sentinel-1 satellite radar data for the Vale of Pickering has been analysed using both SBAS and ISBAS InSAR techniques.

The number of scenes in the ENVISAT data stack for the Vale of Pickering is relatively low therefore the dispersed zones of uplift and subsidence may be due to some atmospheric effects that the processing could not filter out. This increased the uncertainty in the data (i.e. increased standard deviations).

Risks and mitigation measures

No additional risks have been identified.

Discussion of results

The Vale of Pickering ground motion analysis entailed processing three stacks of ERS-1/2, ENVISAT and Sentinel-1 radar satellite data using SBAS and ISBAS techniques (i.e. six levels of analysis in total). The ENVISAT data (2002–2009) consisted of 24 scenes. The SBAS analysis indicated that the urban areas were predominantly stable in the time period. The areas of dispersed motion in the SBAS and ISBAS analyses may be due to atmospheric effects rather than genuine ground surface motion. Nevertheless, the zone of subsidence in the south of the monitoring area is thought to relate to compressible ground.

The ERS-1/2 Vale of Pickering dataset comprised 72 satellite radar scenes and it has therefore not been affected by atmospheric conditions. The SBAS analysis revealed that the urban areas and connecting roads are stable i.e. they are not affected by regional subsidence or uplift between 1992 and 2000. The ISBAS analysis also indicated that the area is predominantly stable apart from three zones that appear to display dispersed uplift. Our experience of this type of dispersed result is that it is not due to geological motion (which is more discrete) but it is most likely due to vegetation changes and agricultural practices.

The Sentinel-1A data offers the opportunity to extend the ground motion monitoring to the present day and beyond. Since April 2016, there has been sufficient Sentinel-1A scenes to carry out InSAR investigation for this area of the UK. It is clear that InSAR processing of this new data results in higher concentration of measurement points using both the SBAS and ISBAS techniques, when compared to ERS and ENVISAT InSAR results.

Within the Sentinel-1A InSAR results there is a great deal of information including an interesting pattern of uplift in the Vale of Pickering, which is most likely linked to the ground water, whether that be at shallow or greater depths.

More research is required to understand the current motion and the cause(s) for it e.g. in relation to hydrogeological controls, current gas extraction and 3D geology. Improved characterisation of the current geological processes and dynamics is required if we are to understand the implications for monitoring through the hydraulic fracturing cycle.

Summary and overall conclusions on baseline monitoring and outcomes

It was apparent at the public engagement event in the Vale of Pickering that the public do not necessarily understand the difference between seismic activity and ground motion. Many link the two and presume that if there is seismic activity there must be ground motion and vice versa. It is therefore important to educate the public and also provide evidence to allay their fears. Part of this is the establishment of a ground motion baseline along with monitoring of the current situation throughout any operations. This baseline allows an understanding of how the natural (and anthropogenic) processes lead to small scale ground motions. The baseline informs the public that small scale motions are continually occurring and do not normally impact on their day to day life. It also offers comfort to the public that there is a record of the existing conditions so that once operations start there is a baseline with which to compare the up to date information.

The unique characteristics of satellite based InSAR have proven it to be a valuable technique in the establishment of a baseline of ground motion for the Vale of Pickering prior to any exploitation of Shale Gas. There are three main benefits of using InSAR to derive ground motions:

1. In common with most remote sensing techniques, InSAR offers a regional view of the phenomena being measured. Ground deformation points are generated for the entire radar scene; this offers the opportunity to not only focus on ground motions for the immediate area surrounding the shale gas site, but also the wider area. This wider view allows an understanding of the processes, which drive the movement of the ground. In the case of the Vale of Pickering if we only focused on a 2 km area around the well site we would not appreciate the link between the extent of the clay and the measured uplift.
2. C-band satellites have been orbiting the Earth, and imaging the UK, since 1992–93. This data has been archived and is freely accessible for anyone to use. It is therefore possible to process the archive data and ‘look back in time’ and retrospectively establish the patterns of ground motion for an area. This is simply not possible with other techniques such as GNSS where the survey equipment must be located on site with knowledge of the phenomena to be measured.
3. InSAR processing results in a dense network of opportunistic measurement points. For techniques such as SBAS the greatest densities are found over urban areas where the built environment act as good radar scatterers. However, recent advances in processing such as ISBAS increase the density of measurements, especially in rural areas, such as the Vale of Pickering. Each measurement point has an average velocity but also a time series, this offers the opportunity to understand how the ground at that point has moved through time thereby enabling the interpretation.

Within the Vale of Pickering C-band SAR data have been used to collect a baseline the ground motion over 25 years and subsequently to characterise the deformation. This baseline shows that overall the area has been stable, but in recent years there has been an area of uplift between Malton and Pickering, which most likely relates to changes in ground water levels. Additional research is required to understand and characterise the current motion and the cause(s) for it e.g. in relation to hydrogeological controls, current gas extraction and 3D geology. The improved characterisation of the current geological processes and dynamics would be very beneficial if an understanding of the implications for monitoring through the hydraulic fracturing cycle is to be reached.