instrumental seismicity recorded from 1999 to 2002. You highlighted (in white) the main event of 11 March 2000 from 1999 to 2002. period earthquake that has affected the upper middle part of the Valley dell'Aniene, which began in March 2000, has attracted some interest, mainly because the seismicity this area is still little known and studied and because the affected area is close to the capital. Following the main event (Md = 4.3 equal to VII MCS), various historical centers of the province of Rome, including the Rock sing, sing, and Cerreto Gerano Laziale reported extensive damage to the heritage historical monuments.
dell'Aniene The Valley is set to a number of tectonic features of which have a direction NW-SE Apennine and part antiappennica NE-SW direction. The geological formations outcropping in the mountains Ruffi (the sector most affected by the seismic sequence) were originally deposited in the transition area between the edge of the carbonate platform "Lazio, Abruzzo and the Marche, Umbria and Sabina facies. These sedimentary successions are characterized mainly by land-Cenozoic limestones and marly limestones. The seismic sequence showed that the western sector of the central been unstable of tectonic character. The area of \u200b\u200bMonti Ruffi is classified in the law concerning the seismic classification of the national territory as an area of \u200b\u200bseismic risk in second category (S = 9). From the literature it appears that the built heritage of the historic centers of the study area is relatively old (before 1919), so even a modest seismicity may affect the extent of vulnerability and seismic risk . The analysis of the seismicity of the area took into account about 150 events which occurred since 1997. In this work, were taken into account the locations of the three-dimensional events (as many of them own part of the seismic sequence of 2000), the seismic energy release in time and statistical evaluations linked to the Gutenberg Richter relationship. This analysis shows a first and important step in the characterization of the seismicity of the area.
Ruffi Mountains are a small chain that is located in the north eastern province of Rome, covering an area of \u200b\u200b70 sq. km. They are delimited (Fig. 1) to the east by the media Aniene Valley, which separates them from Simbruini, south west are bordered by the river that separates them from Fiumicino airport near Mount Prenestini, also bordering to the north west with the mountains Lucretili Sabini, while to the south east border with the Monti-Affilani Ernici. The
Ruffi present with a morphology quite oriented toward the Apennine mountain range NW and SE, while the major peaks are just over 1000 meters of altitude.
The seismic character of this mountain range was known for some time, while there were few details of this interaction with the surrounding areas, in relation to the tectonic structures that characterize this area of \u200b\u200bthe valley of medium-high. TECTONICS OF THE AREA AND GEOLOGICAL FEATURES
The land constituting the Ruffi are sedimentary and were deposited in a 'transition zone', which was located between the carbonate platform, which allowed for the creation of the series 'Lazio, Abruzzo,' and the open sea pelagic environments that enabled the creation of the geological series Umbria Marche Sabino.
We find, therefore, in this sequence Cenozoic calcareous soils and calcareous marl.
The only area that falls outside of this situation is the hill where the old town of Marano Fair. This material consists of limestone and Cretaceous age may be considered as a block of residual carbonate platform margin poc 'even mentioned. The oldest Cenozoic land, are represented by the 'formation of Guadagnolo' of the early Miocene, these are made up of marl organogenic and calcarenites. This training can be found fairly extensive in the northern sector of Ruffi and in the area northwest of Saracinesco, while in the central part it is observable in recordings valleys of rivers that flow into the river Fiumicino. Then there
above the formation of the sequence of Guadagnolo Limestones lithotamnion and bryozoans, which consists of bioclastic calcarenites intercalated with thin layers of terrigenous platform from the area. This formation outcrops in the central and southern mountains Ruffo (Mount Fossicchi, Sun Coast, Monte Cerasolo) on which they were built and developed the main historical area including: Sarcinesco, Cerreto Latium, Anticoli and Corrado.
Following the formation of limestones and bryozoans lithotamnion, due to the changing environment in which they are to re-establish the area of \u200b\u200bopen sea conditions, you have the sedimentation of marls in Orbulina (lower Tortonian). These materials are mainly composed of sedimentary marl and marl limestone outcrops mainly in the central sector of Ruffi alignment along a NW-SE in the resort 'Le Prata' and 'Wolf Source'.
Then there is continuity in the torbitidi siliciclastic sedimentation (also the Tortonian). The latter consist mainly of coarse-grained gray sandstone materials. Note that training it has a discrete thickness is about 500 meters. These materials were formed during the compression phase, which occurred during the Messinian, when the accumulation of terrigenous materials from the areas in lifting diverged by gravity toward the low-lying areas located along the front of the Apennines rising. These materials are observed in siliciclastic paper mainly in the eastern and southern Ruffi.
After surfacing the area of \u200b\u200bthe structure undergoes an erosion of the mountains, by exogenous agents, resulting in filling of depressions by the work of granular materials resulting in substantial deposits that accumulate in areas foothills to form the cones consist of stony materials distributed in a chaotic manner.
are also found in the area, a series of sedimentary material of continental origin such as red soils (derived from the alteration of limestone), travertine levels that in some cases reaching 20 m thick (most likely created as a result of the dam various streams in the area). The mountain range
Ruffi in general presents two zones with different tectonic behavior that can be identified by tracing a line running just north of Fair Sambuci to Marano. The first zone, north of the aforementioned feature, where outcrop sedimentary relatively ductile materials that are part of the formation of Guadagnolo and are characterized by mild anticlines that have a convergence towards the east northeast, in particular, they are observed in the structures of Monte Rotondo and Monte Macchia. Also in the northern sector of Ruffi have been described by some authors (AA.VV., 1998) a series of faults in the east-west.
Moving on to analyze the southern part of the Ruffo, which predominate in the surfacing materials of sedimentary formation known as bryozoans and Limestones lithotamnion, there is a tectonic structure consists of a series of monoclonal crossed with convergence towards the east northeast. Note that the latter have a tendency to lean in close proximity to major faults which have a direction Apennine (NW-SE). Another tectonic element that characterizes the eastern part of the Mountains Ruffi is about the presence of a tectonic alignment Anticoli-Olevano Corrado Romano (Caputo et al., 1974; Damiani, 1982) which represents a zone of intense deformation which occurs along the 'overlapping of Limestones and bryozoans on lithotamnion Torbitidi (Tortonian).
DATA ANALYSIS
historical seismicity
The medium-high Aniene Valley is located in the proximity of important areas such as the seismogenic Fucino, the eagle and the Frusinate. Analysis of parametric catalog of Italian earthquakes (Boschi et al., 1995; Boschi et al., 2000), si nota, che al suo interno non vi ricadono eventi sismici di magnitudo maggiore di 6.
Studi recenti riguardanti la distribuzione delle Massime intensità macrosismiche osservate nei comuni italiani (Molin et al., 1996) indicano, per la zona in oggetto, dei valori intorno all’ottavo grado della scala macrosismica MCS.
Le imprecisioni e la scarsa quantità di notizie, non consentono di definire i parametri degli eventi prima del 1867; da quella data, infatti, iniziava tramite corrispondenza tra Subiaco e l’antico collegio Romano, una raccolta di risentimenti macrosismici per ogni grado d’intensità, l’inizio del catalogo sismico, disponibile per l’Alta Valley of, so it is ascribed to that period. The most important seismic events are shown in Figure A, which shows (Molin et al., 2002) that the first event, which occurred in Subiaco, dating back to 1879, is the fifth MCS. In 1941, Cervara of Rome, there was the strongest event that the catalog overs and that was followed for a couple of weeks, dozens of replicas (Di Filippo, 1943), yet in 1961, in the municipality Rocca di Botte, two events followed one another at a distance of two days, the VI and VII MCS. The last earthquake in chronological order, of which more later, is the latest of 11 March 2000 that hit the area of Canterbury priced VI MCS, this was followed by many replicas.
In summary, the historical seismicity of the Upper Valley dell'Aniene, although poorly documented, can be defined as poor. This fact is confirmed also by the recent inventory of active faults, which do not report the presence in the area (Barchi et al., 2000, Basili et al., 2000; Galadini et al., 2000).
Adapted from: M. Pirro, R. Maro
National Institute of Geophysics and Volcanology - INGV, Rome
Fig A - historical seismicity of the medium-high Valley dell'Aniene
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