California's Napa Valley suffered the biggest earthquake in 25 years in the early hours of August 24, 2014. By processing two Sentinel-1A images, which were acquired on 7 August and 31 August 2014 over the region, an interferogram was generated. The two round shapes around Napa Valley at the top of the image show how the ground moved during the quake. Deformation on the ground causes phase changes in radar signals that appear as the rainbow-coloured patterns. Interferograms like these are being used by scientists on the ground to help them map the surface rupture and model the earthquake. This interferogram very clearly shows the fault that caused the earthquake, which had not been identified as being particularly hazardous prior to the event.