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This study aims to evaluate the possible occurrence during seismic shaking of interaction effects between the shallow subsoil and the overlying buildings of the Villa d'Agri town (Southern Italy). From the geological and building heritage points of view, the investigated area represents a typical town along the Apennines chain and therefore the obtained results could be easily exported to similar urban areas. A total of 239 single-station seismic ambient noise measurements were thus performed, 154 on the urban soils and 85 within buildings. Both subsets of measurements were planned to cover the main outcropping lithologies and building typologies. By means of the Horizontal-to-Vertical Noise Spectral Ratio technique, isofrequency and isoamplitude maps have been reconstructed for the whole area. The results evaluated on the 65 tested buildings allowed to infer the empirical relationship between the first vibrational period, T(s), and their height, H(m). Using this relationship and available information on the height of each building, the first vibrational frequency was estimated for 659 buildings belonging to the urban area of Villa d'Agri. Finally, in order to assess the possible occurrence of the double resonance phenomenon, we compared the main frequency of each building with that interpolated for the underlying foundation soil. The results show that the probability of being affected by the double resonance effect is very high only for a couple of buildings, high for about 16% of the buildings, moderate for the 23% and practically null for most buildings (60%). [ABSTRACT FROM AUTHOR]

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]

A methodological approach based on the integration of different survey techniques may be particularly suitable for the study of areas with complex geology such as those affected by landslide phenomena. The results obtained by the application of combined electrical resistivity tomography (ERT) technique, ambient seismic noise measurements (single station and array), geological investigation and granulometric analysis to characterize and study a landslide occurred on December 3rd, 2013 in Basilicata region (southern Italy) are presented and discussed. The landslide partially affected the peri-urban area of Montescaglioso town and caused damages to small-medium enterprises, infrastructures, and housing. The analysis of ambient noise signals made possible to estimate the depth of the contacts between the main geological formations outcropping in the area and revealed the existence of directional resonance effects. The discontinuities observed by the ERT have confirmed the presence of different lithotypes and allowed illuminating the sliding surface at a depth of about 40 m in agreement with the seismic results and boreholes data. The shallow discontinuities inferred from geophysical surveys were supported also by the results of a detailed granulometric analysis performed on a geognostic survey, confirming the presence of a heterogeneous sedimentary deposit in the area. In such complex context, the acquisition of spatially distributed geophysical properties permitted to increase the knowledge of the geological setting of the area, reaching a level of detail that cannot be observed by applying only a sparse discrete direct sampling. The integration of all the obtained information allowed the delineation of geophysical discontinuities related to the presence of sliding or weakness surfaces and areas with high water content that could contribute to future activation of the movement. This information was crucial to better understand the nature of the landslide, contributing to the planning and the implementation of risk mitigation actions and to the design of remediation works. • Joint geophysics technique to investigation physical/geometric properties of the Montescaglioso landslide. • Seismic ambient noise reveals deep (> ∼200 m) and shallow (∼70-40 m) mechanical contrasts on a large slope. • ERT delineated accurately subsurface topography, heterogeneities, and clayey-water rich layers in the shallow 70 m. • Comparative interpretation of geophysical results point out the recent failure shear-surface at average depth of 40 m. [ABSTRACT FROM AUTHOR]

This work aims at understanding the potential of ambient vibration monitoring in deriving information about material properties change related to landslide seasonal behaviour and resonance directivity in landslides. The case study is the Pietrafitta landslide in southern Italy, known for its effects on the SS87 National Road and for being influenced by artificial vibrations. The field experiment consisted in four two-day-long measurement cycles, completed between April and November 2016, by using two broad-band three components velocimetric stations: one station at the landslide's toe and a reference station outside the landslide. Obtained data were analysed in terms of root mean square, spectral amplitude, horizontal-to-vertical spectral ratio and directionality effects. Results indicated the existence of amplitude daily variations due to vehicular traffic for both the stations, and long-time variations in the amplitudes and frequency content at the landslide site. Polarization and directional resonance showed a daily variation, with the most coherent results in the range of 20° - 60° at the night hours, in the absence of traffic. This azimuthal trend was transverse to the sliding direction. The most marked resonance effect was found in the April recordings. The observed horizontal-to-vertical spectral ratio curves changed over time, due to variation in shear stiffness related to seasonal consolidation. Results from the horizontal-to-vertical spectral ratio inversion suggested a decrease from April to October 2016 in the Vp / Vs ratio, and in the velocity contrast at the base of the sediments consistent with common decrease in landslide activity due to summer drought. • We monitored ambient vibrations at an active landslide in Southern Italy. • We applied HVSR inversion, time-domain polarization, and HVSR directivity methods. • Resonance directivity shows a dominant direction transverse to the landslide sliding. • We attributed the HVSR time variations to variations in the materials properties. [ABSTRACT FROM AUTHOR]

• We propose and test a portable, low-cost reflectometric setup for moisture measurement for cultural heritage application. • A tailored load cell is developed and integrated to increase the reproducibility of measurements. • The application of steady and controlled force decreases the uncertainty of measurements. • The portable device shows high compatibility with other experiments in the literature. • Linear graduation curves between relative humidity and resonant frequency are reported. A low-cost and portable reflectometric system was described to correlate the water content inside building material with the resonance frequency of a planar probe. An inexpensive planar patch resonator was realized, and a high sensitivity load cell was developed to investigate the external force effect on the resonance frequency shift. Regarding the material under test, four stones commonly employed in Italy Cultural Heritage buildings were used: Pietra Gentile, Leccese, Carparo, and Tuff. Measurements were carried out at different water content values and were performed using a portable vector network analyzer. Two different trials were carried out ten times for each moisture level: with an unknown handheld force exerted on the probe and using the load cell to ensure a repeatable force. Results showed that a repeatable applied force guaranteed more reproducible measurements. The achieved humidity/frequency calibration curves can be used, in practice, for non-invasive on-site water content monitoring of historic structures. [ABSTRACT FROM AUTHOR]

A first-order seismic characterization of Northern Apulia (Southern Italy) has been provided by considering geological information and outcomes of a low-cost geophysical survey. In particular, 403 single-station ambient vibration measurements (HVSR techniques) distributed within the main settlements of the area have been considered to extract representative patterns deduced by Principal Component Analysis. The joint interpretation of these pieces of information allows the identification of three main domains (Gargano Promontory, Bradanic Through and Southern Apennines Fold and Thrust Belt), each characterized by specific seismic resonance phenomena. In particular, the Bradanic Through is homogeneously characterized by low frequency (<1 Hz) resonance effects associated with relatively deep (>100 m) seismic impedance, which is contrasting corresponding to the buried Apulian carbonate platform and/or sandy horizons located within the Plio-Pleistocene deposits. In the remaining ones, relatively high frequency (>1 Hz) resonance phenomena are ubiquitous due to the presence of shallower impedance contrasts (<100 m), which do not always correspond to the top of the geological bedrock. These general indications may be useful for a preliminary regional characterization of seismic response in the study area, which can be helpful for an effective planning of more detailed studies targeted to engineering purposes. [ABSTRACT FROM AUTHOR]

This study discusses the effect of buildings vibrations in the urban field in the context of local seismic response studies in order to evaluate the possible occurrence of double resonance effects during strong-motions. The aim is to recognise the interaction effect between near surface geology and all overlying buildings in the urban area of the city of Matera (southern Italy). Single station seismic ambient noise measurements (230) were performed on the main lythologies (134) and on the principal building typologies (96). Soil and building measurements allowed estimating the main frequencies and relative amplitudes of the soil fundamental peaks as well as the first vibrational frequency of buildings. The period-height linear relationship, derived by experimental results, made it possible estimating the fundamental frequency for all the Matera's buildings. Having also estimated the frequencies at each point of the urban soil it was thus possible to obtain a soil-building resonance map in the linear elastic domain. Matera represents an important case study because the first vibration frequency for most of the buildings is quite close to those of the foundation soils. About 21% of buildings show high probability of occurrence of soil-building resonance effect, about 63% of the buildings are characterised by a medium resonance level, while about 16% are at zero or very low level. The proposed approach makes it also possible to identify the areas of the city characterised by these different probabilities of resonance levels. • Empirical evaluation of resonance effect between soils and buildings. • Large single-station ambient noise recordings on main litho- and building types. • A soil-buildings resonance-map as a tool to spot likely critical areas and buildings. • Vibration frequencies of soil and buildings are quite close for most part of the city. • About 21% of buildings show very high probability of resonance with foundation soils. [ABSTRACT FROM AUTHOR]