Rupture Directivity of the Strongest 2016–2017 Central Italy Earthquakes

Abstract

The along-strike rupture directivity of 16 of the strongest earthquakes (4.4 ≤ Mw ≤ 6.5) within the 2016–2017 central Italy seismic sequence is estimated by investigating high-frequency S wave amplitude variations versus source azimuths with an empirical Green's function deconvolution approach. The results confirm that an along-strike rupture directivity is a persistent feature of normal-faulting earthquakes in the Apennines. The preferred rupture directions of the 2016–2017 earthquakes and of similar-magnitude events from the 1997 Umbria-Marche and 2009 L'Aquila-Campotosto seismic sequences show a significant spatial consistency. Different sectors of the Apennines show an alternating trend of preferential along-strike rupture propagation directions with significant spatial and temporal stabilities independent of the magnitude. These results, if confirmed by further data, could lead to more refined hazard assessments of the investigated region.