Structural architecture of the central Apennines: Interpretation of the CROP 11 seismic profile from the Adriatic coast to the orographic divide

Abstract

We present an interpretation of the eastern half portion of the CROP 11 line, a deep reflection seismic profile 265 km long that cuts across the central Apennines from the Tyrrhenian coast to the Adriatic coast. In the study area the line cuts across a pile of thrust sheets that underwent tectonic transport between the Messinian and the Pleistocene. In its easternmost part, the line runs through the Plio‐Pleistocene deposits of the Adriatic foredeep. In the foreland region the CROP 11 line integrates previous information on the crustal structure derived from petroleum exploration and from deep seismic sounding refraction experiments. In particular, the CROP 11 line confirms the existence of a very thick sedimentary sequence underlying the Mesozoic‐Tertiary carbonates of the Apulia Platform interpreted as the Paleozoic‐Triassic sedimentary cover of a pre‐Cambrian crystalline basement. In the mountain chain, where the base thrust of the orogenic wedge reaches a depth of about 25 km, this sedimentary sequence appears to be the deepest geological unit incorporated in the thrust system. This interpretation of the CROP 11 profile suggests an unusual thin‐skin tectonic style implying the detachment from the original basement and the incorporation in the post‐Tortonian tectonic wedge of a very thick Paleozoic‐Triassic sedimentary sequence possibly affected by low‐grade metamorphism in the lower part. Other new suggestions from the CROP 11 seismic data concern the origin of the Fucino basin, one of the most remarkable Plio‐Pleistocene intramontane basins. The normal faults bordering this structural depression, as other important normal faults present in the central Apennines (e.g., the Caramanico fault system in the Majella region), seem to have been controlled by gravitational‐collapse processes driven by uplift during crustal shortening rather than by a generalized extension subsequent to the Apennine compression, as usually reported in the geological literature. If this interpretation is correct, the strong seismic activity in correspondence to the Apennine watershed may be related to the very recent increase in the structural relief caused by an out‐of‐sequence propagation of the active thrusts.

The anatomy of the 2009 L'Aquila normal fault system (central Italy) imaged by high resolution foreshock and aftershock locations

“…These deeply fractured outcropping carbonates over thrust Mio-Pliocene flysch deposits along the northern and eastern margin of the Gran Sasso thrust system [Calamita et al, 2004]. Deep exploration data are not available for the Gran Sasso region, but the CROP11 seismic profile [Patacca et al, 2008], located about 20 km to the south, indicates that the stack of carbonate thrust sheets is up to 8-10 km thick. For the same area seismic tomography and receiver functions studies recover a slightly minor thickness (∼6 km) for the same units.…”

“…During the Liassic extension, central Italy split along the Olevano-Antrodoco tectonic line into two paleotectonic domains (Figure 2): the Lazio-Abruzzo carbonate platform and Umbria-Marche pelagic basin [Castellarin et al, 1982;Calamita and Deiana, 1988;Decandia et al, 1998;Bigi and Pisani, 2005]. The sedimentary cover consists of (from bottom to top): (1) Late Triassic alternated anhydrites and dolomites (e.g., Burano formation) [Martinis and Pieri, 1964;Parotto and Praturlon, 1975]; (2) a 3-4 km thick Jurassic to Paleogene laterally heterogeneous successions mainly deposited on adjacent paleogeographic realms, comprising shallow water platform carbonates as well as local deep basinal successions [Parotto and Praturlon, 1975;Patacca et al, 2008]. The Mio-Pliocene compression was accommodated by first order features such as the OlevanoAntrodoco, the Gran Sasso, the Simbruini, the Teramo and Maiella thrusts (Figure 2), plus minor structures.…”

Shallow subsurface geology and seismic microzonation in a deep continental basin. The Avezzano Town, Fucino basin (central Italy)

“…Both the fault systems have normal kinematics, with left-lateral strike slip component observed for the NW-SE fault system at some intervals during the Quaternary (Galadini and Messina 1994). Seismic reflection and well data show a typical half-graben sedimentary infill in the hanging wall of the Fucino fault system 5 (Cavinato et al 2002;Patacca et al 2008) (Fig. 1b).…”

Spectral-Element Simulations of Seismic Waves Generated by the 2009 L'Aquila Earthquake

“…2). Thus, most of the active faults are normal, comprising a fault system striking northwest-southeast along the Apennines and bounding the basins (e.g., Chiaraluce et al, 2004;Patacca et al, 2008). In particular, the epicentral area corresponds to the upper and middle Aterno valley, with Quaternary lacustrine deposits forming its basins.…”