On 6 April 2009, at 01:32 GMT, an Mw 6.3 seismic event hit the central Apennines, severely damaging the town of L’Aquila and dozens of neighboring villages and resulting in approximately 300 casualties (Istituto Nazionale di Geofisica e Vulcanologia, http://www.ingv.it; MedNet, http://mednet.rm.ingv.it/proce- dure/events/QRCMT/090406_013322/qrcmt.html). This earth- quake was the strongest in central Italy since the devastating 1915 Fucino event (Mw 7.0). The INGV national seismic net- work located the hypocenter 5 km southwest of L’Aquila, 8–9 km deep. Based on this information and on the seismotectonic framework of the region, earthquake geologists traveled to the field to identify possible surface faulting (Emergeo Working Group 2009a, 2009b). The most convincing evidence of pri- mary surface rupture is along the Paganica fault, the geometry of which is consistent with seismological, synthetic aperture radar (SAR) and GPS data. Investigation of other known nor- mal faults of the area, i.e., the Mt. Pettino, Mt. San Franco, and Mt. Stabiata normal faults suggested that these structures were not activated during the April 6 shock (Emergeo Working Group 2009a, 2009b). In this report, we first describe the seismotectonic frame- work of the area, and then we present the field information that supports the occurrence of surficial displacement on the Paganica fault

We measured ground displacements before and after the 2009 L’Aquila earthquake using multi-temporal InSAR techniques to identify seismic precursor signals. We estimated the ground deformation and its temporal evolution by exploiting a large dataset of SAR imagery that spans seventy-two months before and sixteen months after the mainshock. These satellite data show that up to 15 mm of subsidence occurred beginning three years before the mainshock. This deformation occurred within two Quaternary basins that are located close to the epicentral area and are filled with sediments hosting multi-layer aquifers. After the earthquake, the same basins experienced up to 12 mm of uplift over approximately nine months. Before the earthquake, the rocks at depth dilated, and fractures opened. Consequently, fluids migrated into the dilated volume, thereby lowering the groundwater table in the carbonate hydrostructures and in the hydrologically connected multi-layer aquifers within the basins. This process caused the elastic consolidation of the fine-grained sediments within the basins, resulting in the detected subsidence. After the earthquake, the fractures closed, and the deep fluids were squeezed out. The pre-seismic ground displacements were then recovered because the groundwater table rose and natural recharge of the shallow multi-layer aquifers occurred, which caused the observed uplift.

The 2016–2017 seismic sequence, in central Italy, was caused by the Mt. Vettore‐Mt. Bove active fault system, which generated three mainshocks, the largest one of M_w6.6, on 30 October 2016. On 18 January 2017, four M_w5–5.5 seismic events nucleated on the Campotosto active fault. The fault is considered as potentially responsible forM~6.6 seismic events and a seismic gap. The structure also nucleated a M_w5.4 aftershock during the 2009 L'Aquila seismic sequence. We here combined new geological/geomorphological field data, 1945 aerial photographs interpretation, geodetic (Differential Interferometric Synthetic Aperture Radar and Global Positioning System) data, and local historical seismicity analysis to determine how much of the Campotosto seismogenic source ruptured during the 2009 and 2016–2017 seismic sequences. The obtained residual seismic moment of the Campotosto seismic gap is in the range M_w6.4–6.6 earthquake. Moreover, the review of the regional tectonic setting and evolution allowed us a brand new and comprehensive reading of the seismotectonics for the region, in terms of both seismic potential and segmentation of the seismogenic sources, which results strictly connected to the long‐term activity of inherited lithospheric discontinuities, among which the major Ancona‐Anzio fault. We here first highlight that such regional structures strongly influenced the structural setting and evolution of the surrounding regions, in a progressive and continuous process of tectonic inversions, which implies that structural heritage must be understood and considered when dealing with seismotectonics of a given tectonically active region.