Stressing of fault patch during seismic swarms in central Apennines, Italy

Persistent seismic swarms originate along the normal faulting system of central Apennines (Italy). In this study, we analyze the space‐time‐energy distribution of one of the longer and more intense of these swarms, active since August 2013 in the high seismic risk area of the Gubbio basin. Our aim is to verify if information relevant to constraint short‐term earthquake occurrence scenarios is hidden in seismic swarms. During the swarm, the seismic moment release first accelerated, with a rapid migration of seismicity along the fault system, and suddenly dropped. We observe a decrease of the b‐value, along the portion of the fault system where large magnitude events concentrated, possibly indicating that a fault patch was dynamically stressed. This finding suggests that the onset of seismic swarms might help the formation of critically stressed patches. Key Points Space‐time‐energy distribution of seismic swarms on active faults During the swarm, b‐value changes along the active fault Dynamic stress and change in the attitude of fault toward large rupture