San Francisco earthquake risk forecast. Satellite image of California, USA, showing earthquake faults (red lines) and synthetic aperture radar patterns of seismic deformations resulting from a model earthquake on the San Andreas fault (yellow line). The changes in colour represent the displacement of the ground due to the earthquake. The model has estimated that there is a 25 per cent chance of an earthquake measuring magnitude 7 or above in the next 20 years along the San Andreas fault.