Fault‐generated mountain fronts in the central apennines (Central Italy): Geomorphological features and seismotectonic implications

Abstract

The morphotectonic framework of the Central Apennines is given by faulted blocks bounded by normal faults, mostly trending NW-SE, NNW-SSE and NE-SW, which cut previous compressive structures. Such a structural setting is consistent with the focal mechanisms of the earthquakes which often occur in this area.In this paper, three lithologically different normal fault-generated mountain fronts are analysed in order to assess the relations between their geomorphic features and active tectonics. They border the Norcia depression (Sibillini Mts, Umbria), the Amatrice-Campotosto plateau (Laga Mts, Lazio) and the Fucino basin (Marsica Mts, Abruzzi).The Norcia depression is bounded by a N20"W trending normal fault to the east and by a parallel antithetic fault to the west. The main fault has a lo00 m throw and gives rise to a wide fault escarpment, characterized by: (1) sharp slope breaks due to low angle gravity faults; (2) important paleolandslides; and (3) several fault scarplets on the piedmont belt affecting Quaternary deposits.The Amatrice-Campotosto plateau is delimited by the western slope of Mt Gorzano which runs along a N20"W trending normal fault having a 1500 m throw. Minor parallel faults dislocate Quaternary landforms. Large-scale massmovements also occur here.The Fucino basin was struck by the 1915 Avezzano earthquake (I = XI MCS) which produced extensive surface faulting along two parallel NW trending normal fault escarpments on the eastern border of the basin. There is paleoseismic evidence including buried gravity graben in Late Glacial gravels and tectonic dipslip striations on Holocene calcitic crusts covering bedrock normal fault planes.These data suggest that active extensional tectonics plays a major role in the slope morphogenesis of the Central Apennines and they indicate the importance of geomorphic analysis in seismic zonation of this area.

Interactions between mantle upwelling, drainage evolution and active normal faulting: an example from the central Apennines (Italy)

“…The increase in width of the actively extending belt in the central Apennines is also associated with an increase in average elevation and the across‐strike width of the Apennine topographic belt itself. In this central area the eastern normal fault system bounds the Laga and Gran Sasso massifs (Blumetti et al 1993; Giraudi & Frezzotti 1995) and the Sulmona basin (Vittori et al 1995), while the western one starts from the northern end of the l’Aquila basin, crosses the Velino–Sirente massif, bounds the Fucino basin, and continues southward through the Marsica region (Fig. 2).…”

“…The central part of the basin once contained the third largest lake in Italy ( ∼ 150 km 2 ), the last part of which was artificially drained at the end of the 19th century. Seismic reflection profiles and surface geology indicate that the Fucino basin is a half‐graben controlled by a SW‐dipping fault system consisting of three parallel subsidiary faults (Blumetti et al 1993; Cavinato et al 1993a; Messina 1996; Piccardi et al 1999). The fault furthest to the NE juxtaposes Mesozoic bedrock and Plio–Pleistocene continental deposits.…”

Two Tectonic Geomorphology Studies on the Landscape and Drainage Network of Chain and Piedmont Areas of the Abruzzi Region (Central Apennines, Italy)

“…7). The variable degradation of the fault scarps and the morphology of the fault slopes (according to Brancaccio et al, 1978;Wallace, 1978;Blumetti et al, 1993;Bosi et al, 1993;Stewart and Hancock, 1994;Ascione and Cinque, 1997;Peulvast and Vanney, 2001), suggest a variable balance between the relative tectonic uplift, rejuvenating the fault scarps, and the slope denudation processes. Variability of rock resistance seems to have a control on the development of the geomorphic processes influencing the physical weathering because of the different type of stratification, degree of fracturing and local presence of cataclasite.…”

Soil-Gas Geochemistry: Significance and Application in Geological Prospectings

“…The Fucino basin (about 250 square kilometers) is an intramontane tectonic depression located in peninsular Italy within the Apennine chain. The basin is affected by a complex fault network (Nijman, 1971;Giraudi, 1989;Blumetti et al, 1993;Galadini & Messina, 1994) due to an intense Quaternary activity whose most evident geomorphic expression are high mountain fronts. The geometry of these faults and the kinematic indicators, mainly normal or oblique slip, confirm that extensional tectonics has been mainly responsible of the evolution of the basin (Blumetti et al, 1988(Blumetti et al, , 1993Galadini & Messina, 1994) September 1998 The maps show a variability of spatial data continuity over the three years.…”