Active Faulting in Source Region of 2016–2017 Central Italy Event Sequence

Abstract

The Central Italy earthquake sequence produced three main shocks: M6.1 24 August, M5.9 26 October, and M6.5 30 October 2016. Additional M5–5.5 events struck this territory on 18 January 2017 in the Campotosto area. Fault plane solutions for the main shocks exhibit normal faulting (characteristic of crustal extension occurring in the inner central Apennines). Significant evidence, including hypocenter locations, strike and dip angles of the moment tensors, inverted finite fault models (using GPS, interferometric aperture radar, and ground motion data), and surface rupture patterns, all point to the earthquakes having been generated on the Mt. Vettore–Mt. Bove fault system (all three main shocks) and on the Amatrice fault, in the northern sector of the Laga Mountains (portion of 24 August event). The earthquake sequence provides examples of both synthetic and antithetic ruptures on a single fault system (30 October event) and rupture between two faults (24 August event). We describe active faults in the region and their segmentation and present understanding of the potential for linkages between segments (or faults) in the generation of large earthquakes.

Surface Faulting Caused by the 2016 Central Italy Seismic Sequence: Field Mapping and LiDAR/UAV Imaging

“…Bedrock exposed in the Laga and Sibillini Mountains belongs to a multideformed Mesozoic-Cenozoic sedimentary sequence (Umbria-Marche pelagic sequence, mainly limestone to marls), which experienced several tectonic phases prior to the Quaternary seismogenic one (e.g., , Falcucci et al 2018, Ghisetti and Vezzani 1999. Map of surface fault rupture in the Sibillini Mountains, pre-event mapping of Mt.…”

“…Bove fault system (green), finite fault models for all three sequence events (from Galadini et al 2018) Lavecchia et al 1994). Post-orogenic Quaternary and seismogenic active normal faults affect the Neogene Apennine fold-and-thrust belt (Figure 2), which was preceded by Triassic, Jurassic, Cretaceous-Paleogene, and Miocene extension (Castellarin et al 1978, Centamore et al 1971, Elter et al 1975, Falcucci et al 2018, Marchegiani et al 1999, Patacca and Scandone, 1989. This succession of tectonic events, not always coaxial and with different Boncio et al 2004, Pizzi and.…”

“…kinematics, produced highly fractured rock masses and complex zones with multi-reactivated or crosscutting faults. In particular, the geological evolution of the region seems to have been deeply influenced by the multiphase activity of the Ancona-Anzio Line, a lithospheric discontinuity whose kinematic history shaped the structural setting of the region since the Mesozoic to the present (Falcucci et al 2018).…”

“…Bove Massif. Figure 1 shows the general locations of surface rupture in relation to the finite fault models recommended by Galadini et al (2018). The M6.1 24 August event produced surface rupture that extended approximately 5 km north of the southern terminus of the Mt.…”

“…The 2016 Central Italy earthquake sequence occurred in the central portion of the inner Apennine range, in the sector of the Laga and the Sibillini Mountains. These mountains have a complex geological history characterized by multiple phases of tectonic deformation (Falcucci et al 2018, Galadini et al 2018. Despite a lack of historical seismicity, the challenging task of geologic studies to identify locations of active fault segments, long-term fault behavior and kinematic characteristics, and the timing of past ruptures within the Laga and Sibillini Mountains had been undertaken before the 2016 events (e.g., Boncio et al 2004, Cello et al 1997, Galadini and Galli 2000.…”