Seismic sources and stress transfer interaction among axial normal faults and external thrust fronts in the Northern Apennines (Italy): A working hypothesis based on the 1916–1920 time–space cluster of earthquakes

In this study we analyse the main potential seismic sources in some axial and frontal sectors of the Northern Apennines, in Italy. This regionwas hit by a peculiar series of earthquakes that started in 1916 on the external thrust fronts near Rimini. Later, in 1917–1921, seismicity (up to Mw ≈ 6.5) shifted into the axial zone and clearly migrated north-westward, along the belt of active normal faults. The collection of fault-slip data focused on the active normal faults potentially involved in this earthquake series. The acquired data allowed us to better characterize the geometry and kinematics of the faults.