In this paper the tectonic and palaeoseismological significance of the fault scarps present in the massifs of the Velino and of Mount Greco, and in the plains adjacent to these massifs, forming part of the Abruzzo Apennines, is discussed. The basic features of post-glacial fault scarps already mentioned in the literature are illustrated (found in the Fucino Plain, in the Ovindoli-Piani di Pezza area, on the Mount Magnola, in the Valle Majelama alluvial fan and in the Piano di Aremogna). Others not previously mentioned, surveyed by the author, in the Mount Ocre-Cefalone area, in the Piana di Corvaro and on the Mount Greco-Toppe del Tesoro, are also discussed. On the basis of the characteristics of these scarps and of the chronological framework of the last phases of activity of the faults which gave rise to the scarps described, the reliability of the assumptions made for palaeoseismological studies in other places is discussed for the Abruzzo area. The studies performed in the area of the Velino and Greco massifs suggest that, to establish the possible co-seismical activity of the faults, the use of morphological indices (and also of the results obtained with the excavation of trenches) has to be very cautiously applied. It is considered that the following can be stated:. It is probable that the majority of the mentioned fault scarps are co-seismic. In view of the height of some fault scarps, it cannot be excluded that they were formed during the course of earthquake sequences lasting not more that 2-3000 years. It is possible that some of the above mentioned scarps were produced during seismic events of great magnitude. It does not seem possible at present to calculate a precise slip-rate: the amount of the offset often changes along the same fault, even over short distances. Moreover, there are many horst and graben type structures, produced by local effects which contribute towards making an assessment of the fault offsets complicated. It is also clear that erosion can change the aspect of the scarps: an evaluation of the displacements caused by the faults producing them must therefore be made extremely cautiously. Caution is needed in assessing the magnitude of past earthquakes and in assuming recurrence intervals. The dating of the phases of fault activity is approximate, and there is great difficulty in recognizing with any certainty the duration, the sort of activity and the length of the fault segment concerned in the activity. Moreover, the existence in the past of aseismic creep and of movements linked to post-glacial isostatic rebound cannot be excluded with any certainty. These considerations must be regarded for the two massifs examined, since there have been the epicentres of rare earthquakes of low intensity. The only large earthquake known in history, which caused surface ruptures, occurred in the Fucino area in 1915. The fault scarps reported in this paper seem, however, interpretable, in general, as indications of post-glacial tectonic activity, the intensity of which was unsuspected, until a few years ago. © 1994.
All Science Journal Classification (ASJC) codes
- Earth-Surface Processes