This Composite Source straddles the backbone of the central Apennines, including the Montereale Basin (to the northwest), the Middle Aterno Valley, and the Cinque Miglia plain (to the southeast). This Source is a portion of the broad SW-dipping extensional system of the central Apennines, at the passage between the SW-dipping (in Abruzzo) and NE-dipping (in Molise) large normal fault systems from the central to the southern Apennines.
Historical and instrumental catalogues (Boschi et al., 2000; Gruppo di Lavoro CPTI, 2004; Pondrelli et al., 2006; Guidoboni et al., 2007) show a remarkable concentration of damaging and catastrophic earthquakes (plus other intermediate ones) within this area. In particular, the region has been hit by (from NW to SE): the 2 February 1703 (Mw 6.6, Aquilano), the 6 April 2009 (Mw 6.3, L’Aquila), the January 1791 (Mw 5.4, L’Aquila), 24 June 1958 (Mw 5.3, Aquilano), 22 April 1916 (Mw 5.2, Aquilano), 26 November 1461 (Mw 6.5, Aquilano), and the 6 October 1762 (Mw 5.9, Aquilano) earthquakes.
This source includes a number of large segments that have been associated with some key destructive earthquakes among the ones mentioned above -the most recent and best known being the 6 April 2009 L’Aquila event. This earthquake hit a sector of the Central Apennines that was thought to be especially well known from a seismotectonic point of view, also due to a very long history of geological survey and research in the Abruzzi Apennines. However, this event highlighted a spot in the map that had been previously “blank” -but for some authors, e.g. Pace et al. (2006). In fact, Bagnaia et al. (1992) had already identified the Paganica Fault, an apparently minor tectonic element -if compared with the extents of the seismogenic fault associated with the 6 April earthquake and its kinematic parameters.
Unlike for other (much older) neighboring earthquakes (even with larger Mw) that hit this region, the 6 April 2009 has been followed by an unprecedented amount of data and has thus shown a ca. 40° / 55° SW-dipping fault, whose top lies at is ca. 2-3 km below the groundsurface (shown by slip distribution shown by Cirella et al., 2009). These observations has led us to maintain that such dip range and top depth are typical of this fault system, differently from what was previously thought, i.e. 60° dipping that directly crop out in the field -with a coseismic rupture that reaches the groundsurface.
At the southeastern reaches of this Composite Source, the Aremogna-Cinque Miglia fault is thought by D'Addezio et al. (2001) to have caused two events that have occurred on 801 A.D. and on 1349 A.D. (the latter being a large, multiple earthquake that hit 3 different areas of central Italy; see Guidoboni and Comastri, 2005).
Some segments of this Source have been associated with key earthquakes of this region, including pre-historical ones. For an in-depth analysis of seismogenesis in this region, the reader can refer to the Individual Sources in this Database.
The strike of this source was based on that of the mapped structures. The dip was based on geological and geophysical data. The rake represents pure extension, based on geological observations. The minimum and maximum depth were based on geological data and geometrical considerations. The slip rate was inferred from geological observations in adjacent structures that share the same tectonic environment with this Source. The maximum magnitude was taken from that of the largest Individual Source associated.