Monitoring ground surface movements

Underground mining and the pumping of fluids can result in observable displacement of the Earth’s surface. Because the proposed Cornell University Earth Source Heat Project (ESH) would involve pumping fluids in a geothermal reservoir, there is a need to monitor possible displacements of the surface. Such surface movements can be monitored by ground surveying, but the process is labor intensive, limited in spatial extent, and potentially expensive.  Researchers Molan, Pritchard and Lohman have completed a pilot project that shows that an established means to use satellite monitoring of surface movements called Interferometric Synthetic Aperture Radar (InSAR) can be used in Tompkins County, NY. To establish the sensitivity of this method, first they examined the degree of surface movements during years 2018-2021, and then they studied alternative choices of satellite data in order to form recommendations for a program to monitor any impacts of the ESH project.

They used data from two types of satellites: the TerraSAR-X and TanDEM-X (TSX) satellites of the German Space Agency ( X-band, 3.1 cm radar wavelength) and the Sentinel-1 (S1) satellites of the European Space Agency (C-band, 5.6 cm radar wavelength). While the S1 satellites have collected data over Tompkins County for several years as part of their background mission, they had to request and pay for the TSX satellites to collect data over the study area.

The work by Molan, Pritchard and Lohman finds that both S1 and TSX can be used to detect very small amounts of ground deformation in Tompkins County, for which the rates of movement are less than a centimeter per year.  To validate the observations, they compared the measured deformation from the different satellites to each other and found a root mean square difference of 3 mm/yr.  They also find good agreement between the satellite observations and 15 ground control points that were acquired at earlier time periods over an underground salt mine near Lansing, NY (root mean square difference 1.4 mm/yr to 1.92 mm/yr).  Their analysis confirms that ground conditions are sufficient to measure surface deformation using InSAR at the proposed ESH site.

They have shown that satellite InSAR could be useful for monitoring any potential ground displacements from the ESH project.  Considering the level of accuracy and precision observed within our test dataset, they suggest that the ESH project order TSX data (or InSAR data with similar spatial and temporal resolution) for at least the 2-3 year period following the onset of injection activities at the site.

The full report is available here: