The role of stress transfer in earthquake occurrence

An earthquake alters the shear and normal stress on surrounding faults. New evidence strengthens the hypothesis that such small, sudden stress changes cause large changes in seismicity rate. Rates climb where the stress incre ases (aftershocks) and fall where the stress drops. Both increases and decr eases in seismicity rate are followed by a time-dependent recovery. When st ress change is translated into probability change, seismic hazard is seen t o be strongly influenced by earthquake interaction.