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We present a fine-scale shallow geological setting and its possible influence on the seismic building behaviour of L'Aquila downtown which suffered many casualties and building damage caused by the 6 April 2009, Mw 6.1 earthquake. This study draws mainly on the integration of 666 borehole logs and 274 microtremor recordings interpolated with GIS-based techniques. The shallow geology of L'Aquila downtown is characterised by Middle Pleistocene calcareous L'Aquila breccias. Their top surface consists of a weathered epikarst zone that is mantled by Red Soil (reddish colluviated Alfisols) formed during the late Pleistocene. The areal distribution and thickness of Red Soil are causative of the medium microtremor frequency (3–13 Hz). The map of cross-correlation between the medium frequencies, estimated through the empirical Eurocode 8 equation, shows buildings with possible seismic coupling due to the shallow geology setting and the fundamental building period. This technique is further supported by the areal distribution of seismic building damages caused by the 2009 and 1703 L'Aquila earthquakes. This approach, carried out with a large geological and geophysical dataset, is useful in defining seismic site effects and may be effective in mitigating the seismic risk of cities with notable historical heritage in Central Italy, such as the L'Aquila downtown area. [ABSTRACT FROM AUTHOR]

On April 6, 2009, a Mw 6.1 earthquake struck the Plio-Quaternary intermontane L'Aquila-Scoppito Basin in central Italy, causing severe damage to L'Aquila historical downtown and surroundings, which were affected by notable site effects. Previous work has suggested that different site effects may be related to the complex subsurface geologic architecture, given the variable thickness and lithology of L'Aquila-Scoppito Basin filling deposits, on top of which the city was built. To improve the 3D geological model of L'Aquila downtown for seismic site response evaluation and to estimate the seismic hazard of possible buried active normal faults, a multitask project was carried out consisting mainly of the integration of surface geology, geological subsurface datasets and geophysical surveys. Data were interpreted with the aim of creating and building a detailed stratigraphic and tectonic model for the Plio-Quaternary cover of the continental basin and the buried morphology of the Meso-Cenozoic bedrock. We discuss and interpret the results concerning a 1 km-long high-resolution seismic reflection profile and refraction tomography integrated with stratigraphy from deep and shallow boreholes. The results allowed the reconstruction of the Plio-Quaternary succession below L'Aquila downtown. The Plio-Quaternary basin depocentre is located in a minor NNW-SSE graben, an extensional structure within the main regional graben that borders L'Aquila-Scoppito Basin. Finally, data interpretation allowed us to define the subsoil geological model of the study area, to evidence the recent activity of several faults, and to reconstruct the Plio-Quaternary tectono-stratigraphic evolution of the basin. Together, the data are useful to evaluate the seismic hazard of cities with great cultural heritage of central Italy, such as the case study of L'Aquila downtown. [ABSTRACT FROM AUTHOR]

The taxonomy of some non‐marine ostracod assemblages from the Dunarobba Fossil Forest area (south Tiberino Basin, Umbria, Italy) is discussed, adding to the scientific understanding of Piacenzian–Gelasian non‐marine ostracods in central Italy and providing a palaeoenvironmental reconstruction of the shallow coastal lacustrine environments of the Palaeolake Tiberino. The ostracod assemblages include Darwinula stevensoni, Vestalenula cylindrica, Candona (Candona) improvisa, Candona (Neglecandona) neglecta, Candona (Neglecandona) angulata, Candona (Neglecandona) paludinica, Caspiocypris basilicii, Caspiocypris tiberina, Candonopsis kingsleii, Cyclocypris ovum, Ilyocypris bradyi, Ilyocypris decipiens, Cypris mandelstami, Zonocypris membranae quadricella, Potamocypris fulva, Cyprideis crotonensis, Cyprideis rectangularis and two new species: Hemicypris lomastroi sp. nov. and Paralimnocythere turgida sp. nov. In addition to widespread European species, the ostracod assemblages contain some rare species that were previously known from the Pliocene Paludinian Beds of Serbia. A cluster analysis applied to the ostracod frequency matrix has lead to the identification of four separate assemblages that can be attributed to several ecological niches, including emerged hydrosols, ephemeral coastal pools and a littoral lacustrine margin, which suggest a complex coastal environment. [ABSTRACT FROM AUTHOR]

We present the geological map at 1:25,000 scale of the Plio-Quaternary Paganica-San Demetrio-Castelnuovo Basin corresponding to the epicentral area of the 6 April 2009 Mw: 6.29 L'Aquila earthquake. The map focuses on the relationships between the active tectonics and the Plio-Quaternary deposits and on the early evolution of this continental basin. Fine-scale geological field surveys, coupled with paleontological data, facies analyses, well logs and geophysical data interpretation, allowed to better understand the stratigraphy and to review the previously described stratigraphical units, resulting in the definition of eight synthems, spanning from late Piacenzian to Holocene. More precisely, the occurrence of a Caspiocypris species flock (ostracods) at the base of the sedimentary infill of the basin formed by a lacustrine system, suggests that the onset of deposition started in the late Piacenzian. The lacustrine system disappeared around the Gelasian/Calabrian transition, while the subsequent evolution of the sedimentary basin was characterized by the presence of fluvial and alluvial fan systems progressively entrenched into the lake deposits. The results of the above-mentioned activities are summarized in the attached geological map, where the Plio-Quaternary synthems and the active normal faults accountable for the significant seismicity were highlighted. [ABSTRACT FROM AUTHOR]

The Castelnuovo village is placed on a small NW-SE trending ridge, approximately 60 m higher than the valley floor, occupying a portion of the larger continental L'Aquila Basin (Central Italy). During the April 6, 2009 L'Aquila earthquake (M w 6.3), the village suffered heavy damage. Several studies investigated the local seismic amplification of the Castelnuovo area employing geotechnical, geophysical, and geological surveys, together with 1D, 2D and 3D numerical models. However, all these studies relied on shallow geotechnical and geophysical surveys, which do not reach the engineering bedrock and do not constrain the presence of an impedance contrast at depth. To date, no detailed study has been carried out to assess the depth of the engineering bedrock. In this work, we fill this gap by executing two deep boreholes reaching the engineering bedrock, tied with an extensive campaign of microtremor measurements all over the Castelnuovo ridge and the surrounding plain. The interpretation of such new data, together with analytical, numerical, and geostatistical techniques, demonstrates that local seismic amplification is linked to a strong impedance contrast at more than 200-m depth beneath the Castelnuovo village associated with the lithological transition between clayey silts and breccias. Such results differ from those provided by previous studies, where such impedance contrast was considered shallower, and represent a milestone for assessing the local seismic hazard of the area. • Castelnuovo village was completely destroyed during the 2009 L'Aquila earthquake. • Previous studies relied on shallow geotechnical and geophysical measurements only. • New deep boreholes allowed to reconstruct depth of the engineering bedrock. • Microtremor measurements identified a sharp impedance contrast at depth. • Seismic amplification is linked to an impendence contrast at 210-m depth. [ABSTRACT FROM AUTHOR]

Many of the urban settlements in Central Italy are placed nearby active faults and, consequently, the ground motion evaluation and seismic site effects under near-fault earthquakes are noteworthy issues to be investigated. This paper presents the results of site investigations, the seismic site characterization, and the local seismic response for assessing the effects induced by the Mw 6.7 2 February 1703, near-fault earthquake at the Madonna delle Fornaci site (Pizzoli, Central Italy) in which notable ground failure phenomena were observed, as witnessed by several coeval sources. Even though recent papers described these phenomena, the geological characteristics of the site and the failure mechanism have never been assessed through in-situ investigations and numerical modeling. Within a project concerning the assessment of soil liquefaction potential and co-seismic ground failure, deep and shallow continuous core drilling, geophysical investigations and in-hole tests have been carried out. Subsequently, the geotechnical model has been defined and the numerical quantification of the different hypotheses of failure mechanisms has been evaluated. Analyses showed that liquefaction did not occur, and the excess pore water pressure induced by the shaking was not the source of the ground failure. Therefore, it was hypothesized that the sinkhole was likely caused by earthquake-induced gas eruption. [ABSTRACT FROM AUTHOR]

Study of the tectonically active L'Aquila Basin offers new insights into both the creation of the extensional intermontane basins of the central Apennines of Italy and their tectono-sedimentary evolution through time. The combination of large mammal remains, ostracods, molluscs, Mousterian tools, and 14C dating allows better definition of the onset and stratigraphic evolution of the L'Aquila Basin. Interpretation of a seismic reflection profile and well-log data allow evaluation of the subsurface setting of this sedimentary basin and its tectono-sedimentary evolution. The occurrence of a wedge-shaped seismic unit at the base of the basin sedimentary succession defines the first phase of basin fill during a late Piacenzian-Gelasian synrift stage. Activity along the main fault of the extensional fault system responsible for the onset and subsequent development of the western sector of the L'Aquila Basin (L'Aquila-Scoppito subbasin) migrated from southwest to northeast, reaching the presently active Mount Pettino normal fault only in the late Pleistocene-Holocene. The onset of sedimentation in the L'Aquila Basin was synchronous with the onset in the Tiberino Basin, and so the idea that these extensional intermontane basins become progressively younger from the Tyrrhenian toward the Adriatic side of the central Apennines is rejected. In the northern and central Apennines, only two major syndepositional extensional domains can be recognized: a late Miocene rifting area, which includes all the late Miocene extensional basins in Tuscany, and a late Pliocene to earliest Pleistocene rifting area, which possibly includes all the intermontane basins from the Tiberino Basin to the Sulmona Basin. The different time gaps between compressional and extensional deformation at any given locality in the central Apennines could indicate a partial decoupling of processes responsible for the migration of shortening and extension toward the foreland. Diachroneity between the eastward migration of shortening in the foreland and extension in the inner part of the orogen supports the notion that the central Apennines were created as a result of a partially decoupled collision zone. Study of the onset of the central Apennine extensional intermontane basins, together with their seismic activity, indicates that the central Apennine postorogenic extensional domain represents an archive of ~3 m.y. of continued crustal extension. These findings help to refine models of the long-term extensional rate of the central Apennines, and they provide a basis for more reliable seismotectonic models for one of the most seismically active sectors of the central Mediterranean area. [ABSTRACT FROM AUTHOR]