Illustration of the elastic rebound theory of earthquake generation. A, B, and C show the shape of the ground at three different times. The thin vertical line is the fault. A is immediately after the an earthquake on the fault (call it the first earthquake). The green line represents a long straight feature (e.g. a highway, railroad, or power line) built across the fault right after the earthquake. Time B is long after time A. On the San Andreas system, the time interval would be ~150-300 years; for typical faults in Nevada it would be 1,000-10,000 years or more. The straight feature across the fault is deformed. There is energy stored in the rock below the surface, like a stretched spring. The curved part is about 30 km (20 miles) wide. C is immediately after time B, and the second earthquake has just happened, releasing the stored strain energy from the formerly deformed rock near the fault.
