Researchers from Nottingham University have developed software that uses satellite radar data to identify millimetre-scale vertical movements in the landscape in a way that was previously impossible in rural areas.
This could allow landowners, local authorities and fracking firms to identify areas of high seismic activity that may be more likely to produce tremors if hydraulic fracturing (fracking) is used to drill for gas beneath them.
‘What this system gives us is regional coverage so we can see how large areas are moving over time,’ said Dr Colm Jordan from the British Geological Society, who has been working with the Nottingham researchers to validate the software. ‘This gives a more complete picture of what’s happening in rural areas.’
The technique could also be used to monitor whether fracking is causing seismic activity in an area during and after drilling operations – but only if fracking is found to cause surface movement.
‘This system would only look at surface motion, and fracking occurs at great depth,’ said Jordan. ‘If fracking is occurring and it does produce a surface motion this might be one system that could help us monitor that.’
Existing seismic detection systems can use satellite radar data to monitor how the land in urban areas rises or falls due to seismic activity. The time taken for the radar signal to bounce off a fixed object such as a building enables scientists to work out its distance from the satellite, and so over time see if it has moved.
But in rural areas the continual growth of vegetation and the lack of buildings to act as clear reference points over a wide area mean traditional systems were unable to build an accurate picture of the height of the land when viewed from above.
The new software, developed by Dr Andrew Sowter in the Nottingham’s Department of Civil Engineering, uses a technique called Intermittent Small Baseline Subset (ISBAS) to combine over 30 radar images and identify areas of the signal reliable enough to calculate the height of the land.
‘We think that if you look at a forest from the air you can see that the canopy has holes in it that give good measurements from where you can see the ground or dry tree trunks that reflect ground motion,’ he said.
While research from Durham University Energy Institute has found that seismic activity caused by fracking is nearly undetectable by humans, Sowter said there was concern over what might happen from the knock-on effects of injecting fracking fluids into sections of rock that were already under high stress.
A report from the Royal Academy of Engineering has recommended improved monitoring of shale gas exploration sites in order to ensure their safety.
The new software, dubbed “PUNNET GEO”, recently won the overall prize in the European Copernicus Masters Earth Monitoring Competition that recognises innovative uses of satellite observation data.