Intermittent Slip Along the Alto Tiberina Low‐Angle Normal Fault in Central Italy. Issue 17 (4th September 2020)

• Record Type: Journal Article
• Authors: Vuan, A.; Brondi, P.; Sugan, M.; Chiaraluce, L.; Di Stefano, R.; Michele, M.
• Is Part Of: Geophysical research letters. Volume 47:Issue 17(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-04
• Subjects: template matching -- low‐angle normal fault -- central Italy -- microseismicity -- swarms -- Alto Tiberina; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL089039
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The Alto Tiberina normal fault (ATF) in central Italy is a 50‐km‐long crustal structure that dips at a low angle (15–20°). Events on the fault plane are about 10 times less frequent than those located in its shallower syn‐ and antithetic hanging‐wall splays. To enhance ATF catalog and achieve a better understanding of the degree of coupling in the fault system, we apply a template matching technique in the 2010–2014 time window. We augment by a factor 5 the detections and decrease the completeness magnitude to negative values. Contrary to what previously observed on ATF, we highlight intermittent seismic activity and long‐lasting clusters interacting with sequences on the shallower splays. One of these episodes of prolonged seismic activity, detected at the end of 2013 on a 30‐km‐long ATF segment, suggest the ATF active role during an aseismic transient unraveled by geodetic data. Plain Language Summary: 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. Key Points: By template matching we obtain a fivefold increase of the detected events on the Alto Tiberina fault highlighting clusters and swarms From 2010 to 2014, microseismicity is released at variable intermittent rates often interacting with shallow, moderate seismic sequences In 2013, the rise in seismicity suggests an active role of the Alto Tiberina fault during aseismic slip associated with a shallow sequence