Assessing Current Seismic Hazards in Irpinia Forty Years after the 1980 Earthquake: Merging Historical Seismicity and Satellite Data about Recent Ground Movements

Abstract

Recently, a new strain rate map of Italy and the surrounding areas has been obtained by processing data acquired by the persistent scatterers (PS) of the synthetic aperture radar interferometry (InSAR) satellites—ERS and ENVISAT—between 1990 and 2012. This map clearly shows that there is a link between the strain rate and all the shallow earthquakes (less than 15 km deep) that occurred from 1990 to today, with their epicenters being placed only in high strain rate areas (e.g., Emilia plain, NW Tuscany, Central Apennines). However, the map also presents various regions with high strain rates but in which no damaging earthquakes have occurred since 1990. One of these regions is the Apennine sector, formed by Sannio and Irpinia. This area represents one of the most important seismic districts with a well-known and recorded seismicity from Roman times up to the present day. In our study, we merged historical records with new satellite techniques that allow for the precise determination of ground movements, and then derived physical dimensions, such as strain rate. In this way, we verified that in Irpinia, the occurrence of new strong shocks—forty years after one of the strongest known seismic events in the district that occurred on the 23 November 1980, measuring Mw 6.8—is still a realistic possibility. The reason for this is that, from 1990, only areas characterized by high strain rates have hosted significant earthquakes. This picture has been also confirmed by analyzing the historical catalog of events with seismic completeness for magnitude M ≥ 6 over the last four centuries. It is easy to see that strong seismic events with magnitude M ≥ 6 generally occurred at a relatively short time distance between one another, with a period of 200 years without strong earthquakes between the years 1732 and 1930. This aspect must be considered as very important from various points of view, particularly for civil protection plans, as well as civil engineering and urban planning development.

Present‐Day Surface Deformation of Sicily Derived From Sentinel‐1 InSAR Time‐Series

“…Up to now, the use of InSAR data in Sicily has been limited to local investigations, mostly dedicated to the dynamics of Mount Etna (e.g., Bonforte et al., 2011; Borgia et al., 2000; De Novellis et al., 2019; Doin et al., 2011; Froger et al., 2001), and to investigate the kinematics of the Hyblean region (Anzidei et al., 2021; Canova et al., 2012; Vollrath et al., 2017), and southwestern Sicily (Barreca et al., 2014). It was also recently used at a large spatiotemporal scale to quantify transient surface deformations from 1992 to 2014 over the whole Italian territory (Costantini et al., 2017; Piombino et al., 2021). However, newer high resolution spatiotemporal data from Sentinel‐1 satellites can offer more precise mean velocity fields, suitable for tectonic interpretations in regions affected by low to moderate deformation rates.…”

40 Years Later: New Perspectives on the 23 November 1980, Ms 6.9, Irpinia-Lucania Earthquake

“…With regard to the seismological section, the papers presented by Festa et al [40] and Piombino et al [41] starting from the 1980 event, give precise information on the current seismicity. Festa et al [40], provided detailed location and characterization of events of the 3-7 July 2020 Irpinia sequence (southern Italy) that occurred at the northern tip of the main segment that ruptured during the 1980 Irpinia earthquake.…”

“…Piombino et al [41] merged historical records of seismicity with new satellite techniques to allow for the precise determination of ground movements, and then derived physical dimensions, such as strain rate. In this way, the Authors verified that in Irpinia, the occurrence of new strong shocks forty years after the 1980 event (one of the strongest known seismic events in the district) with Mw 6.8 is still a realistic possibility.…”