Seismic Reflection Profiles and Subsurface Geology of the Area Interested by the 2016–2017 Earthquake Sequence (Central Italy)

TLDR

The 2016–2017 Central Italy earthquake sequence involved nine Mw > 5.0 events across a wide area, with geological, geodetic, and seismological data indicating a complex system of NNW‑SSE trending seismogenic normal faults that are well known at the surface and consistent with prior studies. The study aims to reconstruct the subsurface geology near the Norcia Mw 6.5 mainshock using unpublished seismic reflection profiles and geological data to better understand the seismotectonic framework. The authors synthesized all data along a 47 km WSW‑ENE trending geological cross section, interpreting down to 12 km depth. The resulting subsurface model shows that most seismicity is confined to the sedimentary sequence, does not penetrate the basement at 8–11 km depth, and that the seismogenic normal faults transition from high‑angle surface expressions to lower‑angle hypocentral depths, providing insights into the rheology of the seismogenic volume and coseismic deformation.

Abstract

Abstract Starting from 24 August 2016, a long seismic sequence, including nine M w > 5.0 earthquakes, struck a wide area of the Central Italy. A large amount of geological, geodetic, and seismological data envisages a complex system of NNW‐SSE trending, seismogenic normal faults. These active tectonic structures are well known at the surface and consistent with previous seismotectonic studies. In order to improve the comprehension of the seismotectonic framework of this seismic sequence, we provide a novel reconstruction of the subsurface geology of the area close to the Norcia M w 6.5 mainshock (30 October 2016), based on previously unpublished seismic reflection profiles and available geological data. All the data have been synthesized along a 47 km long, WSW‐ENE trending geological cross section, interpreted down to a depth of 12 km. Comparing the subsurface geological model with the available seismological data, we find that the majority of seismicity is confined within the sedimentary sequence and does not penetrate the underlying basement. The basement has been constrained at depths of 8 to 11 km and coincides with the cutoff of the seismicity. We have also traced the trajectories of the seismogenic normal faults activated during this seismic sequence, reconciling the high‐angle (dip>65°) normal faults exposed at the surface, with their angle (dip < 50°) at hypocentral depths. The results of this study may be useful for better understanding the rheological properties of the seismogenic rock volume, as well as the coseismic deformations of the topographic surface observed by geodetic techniques and field mapping.