Caratteristiche della sismicità della zona del Fucino (Italia centrale): Implicazioni sismotettoniche

Abstract

Some studies have been performed aimed at improving the knowledge of the long-term seismicity of the Fucino Plain, which was struck by the Jan. 13th 1915 earthquake (Ms=7, according to Margotti ni et al., 1993). The available seismic catalogues report a very short seismic history not older than 1885. 33 events (probably originated in the investigated area) prior to this date have been discovered; they are mainly related to the 18th century, the older having occurred in 1633. Scarce information is available on the epicentral parametres of these events and therefore only some of them have been reported in the catalogue. As for the characteristics of the seismicity, it is quite clear that without the 1915 event the seismicity would be characterised by earthquakes with Mmax=5, the only exception being the 1904 earthquake (Ms=5.5, according to Margottini et al., 1993). A different distribution during time of the earthquakes which affected the western and eastern sectors of the plain may also be observed. In fact seismic events before and after 1915 affected the former sector, while seismic activity affected the latter sector only in the twenty years after 1915. These seismic characteristics appear to be consistent with the active faulting framework of the Fucino basin, basically a half-graben with a NW-SE axis, whose evolution is driven by the two main active normal faults of the eastern basin border. These primary faults are only responsible for large magnitude earthquakes and related surface faulting, with large recurrence intervals. These large recurrence intervals between surface faulting events are based on the paleoseismological analysis performed by Galadini et al. (1997). Minor faults located in the inner and western portion of the basin are responsible for superficial displacement only when large magnitude events are triggered by the main faults of the eastern basin boundary. The "normal" behaviour of these secondary faults is characterised by a low and distributed in time seismicity.