The paper presents the results of site effects investigation at two villages, Castelvecchio Subequo and Castel di Ieri (Central Italy), located about 2 km from each other, on top of carbonate ridges characterized by complex geological/structural characteristics. Both villages suffered of an anomalous high damage degree determined by the Mw = 6.1, 2009 L'Aquila earthquake, highlighting the occurrence of significant ground motion amplification phenomena. Studying seismic response at rock sites characterized by complex geological setting is a challenging issue, as different factors can alter the expected ground motion. The difficulties arise from both the reconstruction of a suitable and thorough geological/geotechnical subsoil model and limitations of geophysical and numerical methods in such contexts. In order to overcome these difficulties, we here proposed an approach which integrates numerical modelling, based on the definition of a subsoil setting built from an accurate geological field analysis, with active and passive geophysical techniques. In particular, the calibration of numerical models based on transfer functions computed from Standard Spectral Ratio applied to noise recordings provided encouraging results.

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Sample disturbance is still a key issue in offshore investigations, especially when logistic and financial limitations do not allow the use of drilling equipment. This paper focuses on the comparison between the disturbance induced by a conventional free-fall piston corer (FF) and a modified piston corer (AD) equipped with a velocity control (Angel Descent method). Twin core samples were retrieved in two successions of pelitic sediments with a prevailing non-clayey fraction and a non-negligible sandy fraction. Comparison was based on different acquisition, physical and mechanical parameters ranging from accelerometer data to magnetic susceptibility logs and geotechnical parameters from laboratory investigations, including oedometer compression tests and cyclic simple shear tests. Accelerometer data highlighted the sharp reduction in velocity obtained for AD samples. Magnetic susceptibility logs, characterized by a pattern of peaks induced by several volcaniclastic levels present in the succession, indicated that the AD method significantly reduces core shortening. Among geotechnical investigations, cyclic shear tests provided small-strain shear moduli always higher in AD samples, whilst the response of oedometer compression tests was equivocal. In fact, methods for assessing sample disturbance have demonstrated to bear limited effectiveness when applied to soils with relatively low clay content and significant overconsolidation as it is the case of the studied sediments. 1. Introduction Many geotechnical, geological and geophysical analyses for both research and design purposes, require the knowledge of physical and mechanical properties, e.g. undrained shear strength, strength parameters in effective stresses, stiffness and damping parameters. These parameters are affected by soil disturbance induced by the sampling procedure, which is particularly significant in most offshore projects. Lunne et al. (2006) state that block sampling is by far the least invasive method, and that tube sampling unavoidably induces disturbance that alters the sediment structure (including cementation) with negative fallout on a number of geotechnical test results. A further consequence of disturbance induced by gravity and piston coring is core shortening/elongation, which alters the actual depth of geological horizons used for calculating sedimentation rates or reconstructing sub-bottom stratigraphy. Nevertheless, very often deep water investigations are conducted through vessel-operated gravity/piston corers. Sample depths over 0.7 meter below the sea floor (i.e., that reached by spade box corers) require borehole block sampling and hence drilling devices operated from stable structures (pontoons, barge rigs) or drilling vessels. The former can be used when the water depth is shallow, whilst the latter are too expensive for many research projects. In this paper we present and discuss the results of a coring campaign conducted with a standard piston gravity corer and a gravity piston-corer specifically designed to minimize sediment ...

Nowadays, policies addressed to prevention and mitigation of seismic risk need a consolidated methodology finalised to the assessment of local seismic response in explosive volcanic settings. The quantitative reconstruction of the subsoil model provides a key instrument to understand how the geometry and the internal architecture of outcropping and buried geological units have influence on the propagation of seismic waves. On this regard, we present a multidisciplinary approach in the test area of the Stracciacappa maar (Sabatini Volcanic District, central Italy), with the aim to reconstruct its physical stratigraphy and to discuss how subsoil heterogeneities control the 1D and 2D local seismic response in such a volcanic setting. We first introduce a new multidisciplinary dataset, including geological (fieldwork and log from a 45-m-thick continuous coring borehole), geophysical (electrical resistivity tomographies, single station noise measurements, and 2D passive seismic arrays), and geotechnical (simple shear tests performed on undisturbed samples) approaches. Then, we reconstruct the subsoil model for the Stracciacappa maar in terms of vertical setting and distribution of its mechanical lithotypes, which we investigate for 1D and 2D finite element site response analyses through the application of two different seismic scenarios: a volcanic event and a tectonic event. The numerical modelling documents a significant ground motion amplification (in the 1–1.5 Hz range) revealed for both seismic scenarios, with a maximum within the centre of the maar. The ground motion amplification is related to both 1D and 2D phenomena including lithological heterogeneity within the upper part of the maar section and interaction of direct S-waves with Rayleigh waves generated at edges of the most superficial lithotypes. Finally, we use these insights to associate the expected distribution of ground motion amplification with the physical stratigraphy of an explosive volcanic setting, with insights for seismic microzonation studies and local seismic response assessment in populated environments.