Methods of Earth Sciences have been employed in archaeological sites of the Marsica region, central Italy, in two different perspectives: to enhance knowledge on past natural events which damaged/destroyed ancient settlements/monuments and to gather data useful/necessary for preservation of the local cultural heritage. Within this wide perspective, the paper deals with (i) recent archaeoseismological investigations at Alba Fucens and other sites of the Fucino Plain which add evidence of sudden building collapse to the already available (archaeoseismological and paleoseismological) data concerning seismicity of fifth-sixth century AD; (ii) archaeological investigations on remains of the Medieval church of San Bartolomeo showing that coseismic damage in 1349 caused the abandonment of part of the building and its (re)use for burials; (iii) evidence of slope instability which caused rapid mass deposition in the lowest sector of ancient Alba Fucens since around the half of the sixth century AD, inhibiting the occupation of the Roman town; (iv) capable faulting potentially affecting the westernmost sector of the huge hydraulic works made by Romans during the first-second century AD to drain former Lake Fucino.

We investigated the Late Quaternary activity of a major, crustal fault affecting the southern sector of Central Apennines, i.e., the Roveto Valley Fault (also known as Liri Valley fault). This sector of the chain was hit by numerous M>5 historical seismic events. For some of these, e.g., the 1654 one (Mw 6.33), the causative seismogenic source has never been conclusively defined. Within this seismotectonic framework, the recent activity of the Roveto Valley Fault is still a matter of debate. Some authors defined its activity as ended in the Middle Pleistocene; others considered it as currently active and seismogenic at least in its southern portion. We collected new geologic and geomorphologic data along the eastern (left) flank of the Roveto Valley, where the fault crops out, and we identified evidence of displacement of alluvial fans that we attributed to the Early, Middle, and Late Pleistocene. Moreover, the analysis of the relationship between colluvial/detrital deposits, chronologically constrained by means of radiocarbon dating, allowed us to define the activation of the Roveto Valley fault also during historical times, that is, over the past few centuries. Evidence of this has been collected along a large sector of the fault trace for a length of some tens of kilometres. The results of our studies contribute to improve the knowledge of the seismotectonic setting of a large sector of the Central Apennines. Indeed, proving the current activity of the Roveto Valley fault casts new light on possible seismogenic sources of major seismicity of central Italy, potentially responsible for severe damage over a wide area and to relevant cities, Rome being among them.

Surface faulting is, together with strong ground shaking, a hazard associated with major earthquake faults. Assessing surface faulting potential of a given active tectonic structure is a fundamental prerequisite to adequately plan the use of territories and to perform new constructions, in order to act practices aimed to mitigate the associated risk. Assessing the surface faulting potential represents also ground for correctly performing re-construction and retrofitting of buildings and infrastructures during post-earthquake activities. We investigated a branch of a major seismogenic normal fault in the central Apennines of Italy, the Campi-Preci fault, along which the monumental Sant’Eutizio Abbey is located. The medieval Abbey is one of the most important cultural/religious edifices of the central Apennines, heavily damaged by the MW 6.5 October 30, 2016, earthquake, focused a few km to the south. Our study, based on field geological, geomorphological and structural survey and trenching investigations revealed that I) the trace of the Campi-Preci active fault branch is not actually located where presently reported in the available literature, II) the supposed morpho-tectonic features (basically, some km-long scarp carved on the Meso-Cenozoic carbonate bedrock), that suggested the presence of the fault segment in the area of the Sant’Eutizio Abbey, are not related to the active fault but are probably associated to a presently inactive reverse fault and III) the Sant’Eutizio Abbey is likely not potentially affected by primary surface faulting. Our work highlights that only a comprehensive multidisciplinary approach allows to correctly assess surface faulting potential in both seismotectonic and engineering perspectives.

<p>The Seismic Microzonation, as practiced in Italy, consists in defining microzones of the territory affected by homogeneous response to seismic ground shaking, defined as stable zones, vulnerable seismic amplification zones, and unstable zones. In detail, the unstable zones are affected by landslides, soil liquefaction, ground subsidence and surface faulting. In this framework, we conducted a study in the administrative district of L’Aquila (central Italy) aimed at the construction of a new school building, in an area indicated as prone to surface faulting (an active and capable fault was hypothesised in the area) and liquefaction.</p><p>We dug two trenches (named as A and B) perpendicular to the presumed active fault trace. The excavation walls exposed several different continental units mainly characterized by colluvial, organic-rich and “cultural” sediments, as well as paleosols. In trench A, some units, made of sandy-gravelly colluvial deposits, contained abundant pottery fragments, being intensely reworked by very recent human activity. These units were mainly composed of silt and sand sparse with carbonate clasts and directly overlying Middle Pleistocene alluvial deposits. Trench B only exposed units containing pottery fragments and hence pertaining to historical times. Several radiocarbon dating made on charcoal found within these units confirmed the recent age of the deposits, spanning from 25000 to 1800 years before the present. The analysis of the trench walls, the analysis of two boreholes, and field geological investigations revealed the absence of any surface faulting events affecting the stratigraphic sequence of the area, at least since the Middle Pleistocene, likely since the Early Pleistocene. Furthermore, trench B exposed several sedimentary dikes reaching up close to the ground surface, crossing the historical colluvial units, as well as other deformation features typical of liquefaction phenomena. The radiocarbon age determination and the sedimentological characteristics of the units indicate that the most recent liquefaction event occurred after 180 A.D.</p><p>Ultimately, this work represents a “best-practice” case study to investigate the occurrence of geological surface criticalities (such as surface faulting and liquefaction) at specific sites of interest.</p>

<div> <div> <div> <p>Up to now, the complexity and the uncertainty in defining the extent down-dip and along-strike of active faults led to the elaboration of several methods to establish structure 3D geometry. Therefore, different approaches produce different scenarios of seismogenic rupture for the same active tectonic structure. Here we investigate two active fault systems of the central Apennines of Italy: the Roveto Valley Fault and the Laga Mts. Fault. We specifically aim to the understanding of along-strike segmentation of these tectonic structures to contribute to improve the knowledge of the seismotectonic setting of the central Apennines. Overall, our goal is to make a step forward toward the comprehension of the wide theme of seismogenic fault segmentation.</p> <p>The main uncertainties regarding the two fault systems are different. In the case of the Roveto Valley Fault, the uncertainty is twofold: 1) the current activity of the fault is debated; according to some authors, fault activity ended during the Middle Pleistocene, whereas others suggest the fault is still active and seismogenic; 2) the extent of the proposed active section of this tectonic structure is not clearly defined, and this is relevant in a seismotectonic perspective. The Laga Mts. fault system is a complex tectonic structure whose activity is well geologically documented for the southern section of the system; moreover, the fault system played a key role in the seismogenic process of the 2016-2017 central Italy earthquake sequence. Some authors interpret the fault as the surface expression of a single large seismogenic source, capable of generating seismic events of Mw ≈ 6.7. Other authors, instead, propose that this system consists in two structurally aligned but kinematically independent faults, the Amatrice and Campotosto faults. Following the 2016-2017 seismic sequence, an important debate is taking place within the scientific community about the definition of 1) the individual seismogenic sources that make up the Laga Mts. fault system and 2) the geometric and kinematic relationship between the fault(s) at surface and its (their) possible prolongation at depth as crustal major seismogenic sources.</p> <p>Through morphological, morphotectonic and structural analyses we propose segmentation criteria and possible segmentation scenarios for these two structures. These allow us to estimate the maximum coseismic rupture and the maximum magnitude expected from a single seismic event for the investigated fault, improving the seismotectonic knowledge of the central Apennines.</p> </div> </div> </div>