Intermittent Slip Along the Alto Tiberina Low-Angle Normal Fault in Central Italy

Small magnitude events have regularly shaken the 50-km-long Alto Tiberina low-angle normal fault (ATF) in central Italy. Above it, few kilometers long syn- and antithetic higher-angle normal faults were active with many moderate seismic sequences and 10 times more events than ATF between 2010 and 2014. To better understand the fault system interaction, we apply a technique for finding events which match predefined templates to improve the ATF seismic catalog. The results indicate that productive sequences in the shallower high-angle faults often hamper the detection of microseismicity along with the ATF and that events are released at intermittent rates. Moreover, the seismic activity is mainly organized in clusters of small earthquakes lasting days or months with no identifiable mainshock. These clusters span a 30-km-long segment and coincide with transient deformation recorded at the end of 2013.