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Poggi, Valerio
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Poggi, Valerio
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- PublicationRestrictedGuidelines for the good practice of surface wave analysis: a product of the InterPACIFIC project(2018)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; ;Surface wave methods gained in the past decades a primary role in many seismic projects. Specifically, they are often used to retrieve a 1D shear wave velocity model or to estimate the VS,30 at a site. The complexity of the interpretation process and the variety of possible approaches to surface wave analysis make it very hard to set a fixed standard to assure quality and reliability of the results. The present guidelines provide practical information on the acquisition and analysis of surface wave data by giving some basic principles and specific suggestions related to the most common situations. They are primarily targeted to non-expert users approaching surface wave testing, but can be useful to specialists in the field as a general reference. The guidelines are based on the experience gained within the InterPACIFIC project and on the expertise of the participants in acquisition and analysis of surface wave data.204 5 - PublicationOpen AccessSeismo-stratigraphic model of the Po Plain (Italy)(2019-09-18)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The aim of this study is to provide a seismo-stratigraphic model of the Po Plain sedimentary basin (Northern Italy), to be implemented in soil hazard studies at regional scale. The proposed model characterizes the subsoil up to the seismic bedrock depth. Mascandola et al. (2018) identifies the seismic bedrock of the Po Plain in correspondence with a marked increase in the mechanical properties of the subsoil materials, which produces a measurable resonance effect at the surface in the medium-to-long-period range. To map the seismic bedrock depth we relies on an extensive collection of both existing and newly acquired ambient vibration measurements, with the aim of defining the soil resonance frequencies and the shear-wave velocity gradients within the soft sediments above seismic bedrock. Based on the collected data, an empirical regression model that relates the thickness of the soil deposits above the seismic bedrock to their resonant frequency is defined and applied to map the seismic bedrock depth in the Po Plain area. The resultant seismic bedrock map is correlated with depth of the main unconformities recognized inside the Quaternary succession (Regione Emilia-Romagna,ENI–AGIP, 1998; Regione Lombardia, Eni Divisione Agip,2002). The shear-wave velocity model above seismic bedrock is derived through the interpolation of 51 S-wave velocity profiles selected after a quality check on the available data. The velocity gradients highlights two different zones inside the study area: one at Northwest and another at East-Southeast with higher and lower velocity gradients respectively. To compute the soil amplification functions, the velocity model is discretized into a grid. For each grid node, a 1D soil model is defined and a numerical ground response analysis is carried out. The gridded soil amplification model is checked at those sites with both borehole and surface seismic sensors by comparing the theoretical and empirical soil amplification functions. These results will be included in regional seismic hazard studies, to account for soil amplification in seismic hazard estimates.118 142 - PublicationRestrictedMapping the Seismic Bedrock of the Po Plain (Italy) through Ambient‐Vibration Monitoring(2019)
; ; ; ; ; ; ; ; ; ; ; ; ; In earthquake engineering, “engineering bedrock” is regarded as a stiff material (i.e., rock or rock-like geological formation) that is characterized by a shearwave velocity greater than a target value (e.g., 800 m=s; current Italian and European seismic codes). In the case of deep basins, the identification of engineering bedrock is problematic, because it can lie well below the penetration depth of most common prospecting methods (i.e., a few tens of meters). Moreover, the depth of engineering bedrock might not represent an effective proxy of the sedimentary thickness responsible for site amplification. The Po Plain sedimentary basin (northern Italy) is one of the deepest and widest worldwide, and it presents such problems. The aim of this work is to estimate the sedimentary thickness responsible for ground-motion amplification at medium and long periods in the Po Plain. Passive seismic prospecting methods based on ambient-vibration measurements using single-station and array configurations were considered to map “seismic bedrock” depth. This corresponds to a marked seismic impedance contrast where the shear-wave velocity approached, or exceeded, 800 m=s. In the latter case, seismic and engineering bedrocks coincided. Our mapping will be useful for future site response assessments, numerical modeling of seismicwave propagation, dynamic ground response analyses, and site-specific seismic hazard evaluation at the basin scale.562 30 - PublicationRestrictedAn inter-disciplinary and multi-scale approach to assess the spatial variability of ground motion for seismic microzonation: the case study of Cavezzo municipality in Northern Italy(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Seismic microzonation represents a basic tool for prevention activity planning and land management. An extensive and detailed microzonation study was performed with reference to the territory of the Municipality of Cavezzo, damaged during the seismic sequence hitting Emilia-Romagna Region, Northern Italy, in 2012. In this paper, we discuss the work carried out to characterize the spatial variability of ground motion amplification due to local soil conditions in the municipality area. An inter- and multi-disciplinary approach is presented, involving geotechnical engineers, geophysicists, geologists and seismologists from different institutions, to thoroughly characterize the territory using complementary techniques with different level of resolution and confidence. A considerable amount of geomorphological, geological, hydrogeological, seismological, geotechnical and geophysical investigations was collected and processed for the purpose. A GIS-based (Geographic Information System) platform was initially setup to manage the gathered data, which now includes the results of about 1000 geotechnical and geophysical tests. Such an extended dataset was then used as a primary constraint for the creation of a comprehensive pseudo-3D geotechnical and seismo-stratigraphic model of the territory, consisting of a dense grid of one-dimensional vertical profiles to depict the variability of the soil properties over the area. The model was finally used as input for linear-equivalent ground response analysis. For the calculation of the amplification factors, special emphasis was given to the treatment and propagation of the uncertainties of the model parameters, whose different realizations have been accounted through a logic tree approach.295 4